Replace \r\n with Environment.NewLine (#887)

Replace Windows specific newline characters with Environment.Newline in some unit tests

Author: rohahn

UnitsNet.Serialization.JsonNet.Tests/UnitsNetBaseJsonConverterTest.cs

@@ -44,7 +44,7 @@ public void UnitsNetBaseJsonConverter_ConvertIQuantity_throws_ArgumentNullExcept
         {
             var result = Assert.Throws<ArgumentNullException>(() => _sut.Test_ConvertDoubleIQuantity(null));
 
-            Assert.Equal("Value cannot be null.\r\nParameter name: quantity", result.Message);
+            Assert.Equal($"Value cannot be null.{Environment.NewLine}Parameter name: quantity", result.Message);
         }
 
         [Fact]

UnitsNet.Serialization.JsonNet.Tests/UnitsNetIComparableJsonConverterTest.cs

@@ -49,7 +49,7 @@ public void UnitsNetIComparableJsonConverter_ReadJson_throws_ArgumentNullExcepti
         {
             var exception = Assert.Throws<ArgumentNullException>(() => _sut.ReadJson(reader, typeof(IQuantity), null, false, serializer));
 
-            Assert.Equal($"Value cannot be null.\r\nParameter name: {paramName}", exception.Message);
+            Assert.Equal($"Value cannot be null.{Environment.NewLine}Parameter name: {paramName}", exception.Message);
         }
 
         [Fact]

UnitsNet.Serialization.JsonNet.Tests/UnitsNetIQuantityJsonConverterTest.cs

@@ -39,7 +39,7 @@ public void
         {
             var exception = Assert.Throws<ArgumentNullException>(() => _sut.WriteJson(writer, Power.FromWatts(10D), serializer));
 
-            Assert.Equal($"Value cannot be null.\r\nParameter name: {parameterName}", exception.Message);
+            Assert.Equal($"Value cannot be null.{Environment.NewLine}Parameter name: {parameterName}", exception.Message);
         }
 
         [Fact]
@@ -104,7 +104,7 @@ public void UnitsNetIQuantityJsonConverter_ReadJson_throws_ArgumentNullException
         {
             var exception = Assert.Throws<ArgumentNullException>(() => _sut.ReadJson(reader, typeof(IQuantity), null, false, serializer));
 
-            Assert.Equal($"Value cannot be null.\r\nParameter name: {paramName}", exception.Message);
+            Assert.Equal($"Value cannot be null.{Environment.NewLine}Parameter name: {paramName}", exception.Message);
         }
 
         [Fact]