Update System.Text.Json converter source links to main branch (#49670)

Author: Copilot

docs/standard/serialization/system-text-json/converters-how-to.md

@@ -70,7 +70,7 @@ The following steps explain how to create a converter by following the basic pat
 * Override the `Write` method to serialize the incoming object of type `T`. Use the <xref:System.Text.Json.Utf8JsonWriter> that is passed to the method to write the JSON.
 * Override the `CanConvert` method only if necessary. The default implementation returns `true` when the type to convert is of type `T`. Therefore, converters that support only type `T` don't need to override this method. For an example of a converter that does need to override this method, see the [polymorphic deserialization](#support-polymorphic-deserialization) section later in this article.
 
-You can refer to the [built-in converters source code](https://github.com/dotnet/runtime/tree/81bf79fd9aa75305e55abe2f7e9ef3f60624a3a1/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/) as reference implementations for writing custom converters.
+You can refer to the [built-in converters source code](https://github.com/dotnet/runtime/tree/main/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters/) as reference implementations for writing custom converters.
 
 ## Steps to follow the factory pattern
 
@@ -228,7 +228,7 @@ For scenarios that require type inference, the following code shows a custom con
 
 The example shows the converter code and a `WeatherForecast` class with `object` properties. The `Main` method deserializes a JSON string into a `WeatherForecast` instance, first without using the converter, and then using the converter. The console output shows that without the converter, the run-time type for the `Date` property is `JsonElement`; with the converter, the run-time type is `DateTime`.
 
-The [unit tests folder](https://github.com/dotnet/runtime/tree/c72b54243ade2e1118ab24476220a2eba6057466/src/libraries/System.Text.Json/tests/Serialization/) in the `System.Text.Json.Serialization` namespace has more examples of custom converters that handle deserialization to `object` properties.
+The [unit tests folder](https://github.com/dotnet/runtime/tree/main/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/CustomConverterTests) in the `System.Text.Json.Serialization` namespace has more examples of custom converters that handle deserialization to `object` properties.
 
 ### Support polymorphic deserialization
 
@@ -364,18 +364,18 @@ When you use <xref:System.Text.Json.Serialization.ReferenceHandler.Preserve%2A>,
 
 The [Migrate from Newtonsoft.Json to System.Text.Json](migrate-from-newtonsoft.md) article contains additional samples of custom converters.
 
-The [unit tests folder](https://github.com/dotnet/runtime/blob/81bf79fd9aa75305e55abe2f7e9ef3f60624a3a1/src/libraries/System.Text.Json/tests/Serialization/) in the `System.Text.Json.Serialization` source code includes other custom converter samples, such as:
+The [unit tests folder](https://github.com/dotnet/runtime/tree/main/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/CustomConverterTests) in the `System.Text.Json.Serialization` source code includes other custom converter samples, such as:
 
-* [Int32 converter that converts null to 0 on deserialize](https://github.com/dotnet/runtime/blob/81bf79fd9aa75305e55abe2f7e9ef3f60624a3a1/src/libraries/System.Text.Json/tests/Serialization/CustomConverterTests.NullValueType.cs)
-* [Int32 converter that allows both string and number values on deserialize](https://github.com/dotnet/runtime/blob/81bf79fd9aa75305e55abe2f7e9ef3f60624a3a1/src/libraries/System.Text.Json/tests/Serialization/CustomConverterTests.Int32.cs)
-* [Enum converter](https://github.com/dotnet/runtime/blob/81bf79fd9aa75305e55abe2f7e9ef3f60624a3a1/src/libraries/System.Text.Json/tests/Serialization/CustomConverterTests.Enum.cs)
-* [List\<T> converter that accepts external data](https://github.com/dotnet/runtime/blob/81bf79fd9aa75305e55abe2f7e9ef3f60624a3a1/src/libraries/System.Text.Json/tests/Serialization/CustomConverterTests.List.cs)
-* [Long[] converter that works with a comma-delimited list of numbers](https://github.com/dotnet/runtime/blob/81bf79fd9aa75305e55abe2f7e9ef3f60624a3a1/src/libraries/System.Text.Json/tests/Serialization/CustomConverterTests.Array.cs)
+* [Int32 converter that converts null to 0 on deserialize](https://github.com/dotnet/runtime/blob/main/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/CustomConverterTests/CustomConverterTests.NullValueType.cs)
+* [Int32 converter that allows both string and number values on deserialize](https://github.com/dotnet/runtime/blob/main/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/CustomConverterTests/CustomConverterTests.Int32.cs)
+* [Enum converter](https://github.com/dotnet/runtime/blob/main/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/CustomConverterTests/CustomConverterTests.Enum.cs)
+* [List\<T> converter that accepts external data](https://github.com/dotnet/runtime/blob/main/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/CustomConverterTests/CustomConverterTests.List.cs)
+* [Long[] converter that works with a comma-delimited list of numbers](https://github.com/dotnet/runtime/blob/main/src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/CustomConverterTests/CustomConverterTests.Array.cs)
 
-If you need to make a converter that modifies the behavior of an existing built-in converter, you can get [the source code of the existing converter](https://github.com/dotnet/runtime/tree/81bf79fd9aa75305e55abe2f7e9ef3f60624a3a1/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters) to serve as a starting point for customization.
+If you need to make a converter that modifies the behavior of an existing built-in converter, you can get [the source code of the existing converter](https://github.com/dotnet/runtime/tree/main/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters) to serve as a starting point for customization.
 
 ## Additional resources
 
-* [Source code for built-in converters](https://github.com/dotnet/runtime/tree/81bf79fd9aa75305e55abe2f7e9ef3f60624a3a1/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters)
+* [Source code for built-in converters](https://github.com/dotnet/runtime/tree/main/src/libraries/System.Text.Json/src/System/Text/Json/Serialization/Converters)
 * [System.Text.Json overview](overview.md)
 * [How to serialize and deserialize JSON](how-to.md)