Bump MSTest.TestFramework

Bumps the dotnet group with 1 update in the /docs/csharp/language-reference/operators/snippets/shared directory: [MSTest.TestFramework](https://github.com/microsoft/testfx).


Updates `MSTest.TestFramework` from 3.5.2 to 3.6.4
- [Release notes](https://github.com/microsoft/testfx/releases)
- [Changelog](https://github.com/microsoft/testfx/blob/main/docs/Changelog.md)
- [Commits](microsoft/testfx@v3.5.2...v3.6.4)

---
updated-dependencies:
- dependency-name: MSTest.TestFramework
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: dotnet
...

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

docs/csharp/language-reference/operators/snippets/shared/operators.csproj

@@ -10,7 +10,7 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="MSTest.TestFramework" Version="3.5.2" />
+    <PackageReference Include="MSTest.TestFramework" Version="3.6.4" />
   </ItemGroup>
 
 </Project>