Bump MSTest.TestAdapter from 3.0.4 to 3.1.1

Bumps [MSTest.TestAdapter](https://github.com/microsoft/testfx) from 3.0.4 to 3.1.1.
- [Release notes](https://github.com/microsoft/testfx/releases)
- [Changelog](https://github.com/microsoft/testfx/blob/main/docs/Changelog.md)
- [Commits](microsoft/testfx@v3.0.4...v3.1.1)

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

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

src/ApprovalTests.MSTest/ApprovalTests.MSTest.csproj

@@ -7,7 +7,7 @@
   <ItemGroup>
     <Using Remove="System.Net.Http" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.6.3" />
-    <PackageReference Include="MSTest.TestAdapter" Version="3.0.4" />
+    <PackageReference Include="MSTest.TestAdapter" Version="3.1.1" />
     <PackageReference Include="MSTest.TestFramework" Version="3.0.4" />
     <ProjectReference Include="..\ApprovalUtilities\ApprovalUtilities.csproj" />
     <ProjectReference Include="..\ApprovalTests\ApprovalTests.csproj" />