Bump MSTest.TestAdapter from 3.1.1 to 3.2.1

Bumps [MSTest.TestAdapter](https://github.com/microsoft/testfx) from 3.1.1 to 3.2.1.
- [Release notes](https://github.com/microsoft/testfx/releases)
- [Changelog](https://github.com/microsoft/testfx/blob/main/docs/Changelog.md)
- [Commits](microsoft/testfx@v3.1.1...v3.2.1)

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

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

StreamRegex.Tests/StreamRegex.Tests.csproj

@@ -10,7 +10,7 @@
     <ItemGroup>
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
         <PackageReference Include="MSTest.TestFramework" Version="3.2.0" />
-        <PackageReference Include="MSTest.TestAdapter" Version="3.1.1" />
+        <PackageReference Include="MSTest.TestAdapter" Version="3.2.1" />
     </ItemGroup>
 
     <ItemGroup>