Bump the dotnet group across 1 directory with 2 updates

Bumps the dotnet group with 2 updates in the /docs/core/tutorials/snippets/library-with-visual-studio/csharp directory: [coverlet.collector](https://github.com/coverlet-coverage/coverlet) and [MSTest](https://github.com/microsoft/testfx).


Updates `coverlet.collector` from 6.0.2 to 6.0.3
- [Release notes](https://github.com/coverlet-coverage/coverlet/releases)
- [Commits](coverlet-coverage/coverlet@v6.0.2...v6.0.3)

Updates `MSTest` from 3.6.1 to 3.7.1
- [Release notes](https://github.com/microsoft/testfx/releases)
- [Changelog](https://github.com/microsoft/testfx/blob/main/docs/Changelog.md)
- [Commits](microsoft/testfx@v3.6.1...v3.7.1)

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

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

docs/core/tutorials/snippets/library-with-visual-studio/csharp/StringLibraryTest/StringLibraryTest.csproj

@@ -7,8 +7,8 @@
   </PropertyGroup>
 
   <ItemGroup>
-    <PackageReference Include="MSTest" Version="3.6.1" />
-    <PackageReference Include="coverlet.collector" Version="6.0.2">
+    <PackageReference Include="MSTest" Version="3.7.1" />
+    <PackageReference Include="coverlet.collector" Version="6.0.3">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>