Bump MSTest.TestFramework from 3.6.3 to 3.8.3

Bumps [MSTest.TestFramework](https://github.com/microsoft/testfx) from 3.6.3 to 3.8.3.
- [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...v3.8.3)

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

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

Author: dependabot[bot]

Directory.Packages.props

@@ -117,7 +117,7 @@
     <PackageVersion Include="coverlet.collector" Version="6.0.2" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
     <PackageVersion Include="MSTest.TestAdapter" Version="3.6.3" />
-    <PackageVersion Include="MSTest.TestFramework" Version="3.6.3" />
+    <PackageVersion Include="MSTest.TestFramework" Version="3.8.3" />
     <PackageVersion Include="Avalonia.Headless.XUnit" Version="$(AvaloniaVersion)" />
     <PackageVersion Include="Verify" Version="26.1.2" />
     <PackageVersion Include="Verify.CommunityToolkit.Mvvm" Version="0.1.0" />