Bump the dotnet group (#44932)

Bumps the dotnet group in /docs/core/testing/snippets/unit-testing-using-mstest/csharp/PrimeService.Tests with 2 updates: [MSTest.TestAdapter](https://github.com/microsoft/testfx) and [MSTest.TestFramework](https://github.com/microsoft/testfx).


Updates `MSTest.TestAdapter` from 3.7.3 to 3.8.0
- [Release notes](https://github.com/microsoft/testfx/releases)
- [Changelog](https://github.com/microsoft/testfx/blob/main/docs/Changelog.md)
- [Commits](microsoft/testfx@v3.7.3...v3.8.0)

Updates `MSTest.TestFramework` from 3.7.3 to 3.8.0
- [Release notes](https://github.com/microsoft/testfx/releases)
- [Changelog](https://github.com/microsoft/testfx/blob/main/docs/Changelog.md)
- [Commits](microsoft/testfx@v3.7.3...v3.8.0)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]