Bump MSTest.TestAdapter from 3.0.2 to 3.1.1 in /Source (#16)

Bumps [MSTest.TestAdapter](https://github.com/microsoft/testfx) from 3.0.2 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@v3.0.2...v3.1.1)

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

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

Source/Tests/Singulink.Collections.Tests/Singulink.Collections.Tests.csproj

@@ -5,7 +5,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.5.0" />
-    <PackageReference Include="MSTest.TestAdapter" Version="3.0.2" />
+    <PackageReference Include="MSTest.TestAdapter" Version="3.1.1" />
     <PackageReference Include="MSTest.TestFramework" Version="3.0.2" />
     <PackageReference Include="coverlet.collector" Version="6.0.0">
       <PrivateAssets>all</PrivateAssets>

Source/Tests/Singulink.Collections.Weak.Tests/Singulink.Collections.Weak.Tests.csproj

@@ -5,7 +5,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.5.0" />
-    <PackageReference Include="MSTest.TestAdapter" Version="3.0.2" />
+    <PackageReference Include="MSTest.TestAdapter" Version="3.1.1" />
     <PackageReference Include="MSTest.TestFramework" Version="3.0.2" />
     <PackageReference Include="coverlet.collector" Version="6.0.0">
       <PrivateAssets>all</PrivateAssets>