Update Microsoft.CodeAnalysis.NetAnalyzers requirement from 5.* to 6.*

Updates the requirements on [Microsoft.CodeAnalysis.NetAnalyzers](https://github.com/dotnet/roslyn-analyzers) to permit the latest version.
- [Release notes](https://github.com/dotnet/roslyn-analyzers/releases)
- [Changelog](https://github.com/dotnet/roslyn-analyzers/blob/main/PostReleaseActivities.md)
- [Commits](https://github.com/dotnet/roslyn-analyzers/commits)

---
updated-dependencies:
- dependency-name: Microsoft.CodeAnalysis.NetAnalyzers
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Directory.Build.props

@@ -26,7 +26,7 @@
   <ItemGroup Condition="'$(Configuration)'=='Debug'">
     <!--<Compile Update="**\*.cs" DependentUpon="I%(Filename).cs" />-->
     <PackageReference Include="stylecop.analyzers" Version="1.*" PrivateAssets="all" />
-    <PackageReference Include="Microsoft.CodeAnalysis.NetAnalyzers" Version="5.*" PrivateAssets="all" />
+    <PackageReference Include="Microsoft.CodeAnalysis.NetAnalyzers" Version="6.*" PrivateAssets="all" />
     <PackageReference Include="Roslynator.Analyzers" Version="3.*" PrivateAssets="All" />
     <AdditionalFiles Include="$(MSBuildThisFileDirectory)stylecop.json" Link="stylecop.json" />
   </ItemGroup>