Remove extra newline from APIDiff TOC (#49794)

Author: ericstj

src/Compatibility/ApiDiff/Microsoft.DotNet.ApiDiff/FileOutputDiffGenerator.cs

@@ -155,8 +155,6 @@ public async Task RunAsync(CancellationToken cancellationToken)
             _log.LogMessage($"Wrote '{filePath}'.");
         }
 
-        tableOfContents.AppendLine();
-
         string tableOfContentsFilePath = Path.Combine(_outputFolderPath, $"{_tableOfContentsTitle}.md");
 
         if (_writeToDisk)

test/Microsoft.DotNet.ApiDiff.Tests/Diff.Disk.Tests.cs

@@ -25,7 +25,6 @@ Lines preceded by a '+' are additions and a '-' indicates removal.
 
         * [{DefaultAssemblyName}]({DefaultTableOfContentsTitle}_{DefaultAssemblyName}.md)
 
-
         """;
 
     private const string ExpectedEmptyTableOfContents = $"""
@@ -35,7 +34,6 @@ API listing follows standard diff formatting.
         Lines preceded by a '+' are additions and a '-' indicates removal.
 
 
-
         """;
 
     private const string BeforeCode = """
@@ -239,7 +237,6 @@ Lines preceded by a '+' are additions and a '-' indicates removal.
 
 * [Assembly1]({DefaultTableOfContentsTitle}_Assembly1.md)
 * [Assembly2]({DefaultTableOfContentsTitle}_Assembly2.md)
-
 ";
 
         using TempDirectory inputFolderPath = new();