Bump MSTest from 3.6.3 to 3.6.4 in the microsoft group

Bumps the microsoft group with 1 update: [MSTest](https://github.com/microsoft/testfx).


Updates `MSTest` from 3.6.3 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@v3.6.3...v3.6.4)

---
updated-dependencies:
- dependency-name: MSTest
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: microsoft
...

Signed-off-by: dependabot[bot] <[email protected]>

Directory.Packages.props

@@ -2,6 +2,6 @@
   <ItemGroup>
     <PackageVersion Include="BenchmarkDotNet" Version="0.14.0" />
     <PackageVersion Include="Microsoft.CodeAnalysis.CSharp" Version="4.12.0-3.final" />
-    <PackageVersion Include="MSTest" Version="3.6.3" />
+    <PackageVersion Include="MSTest" Version="3.6.4" />
   </ItemGroup>
 </Project>