Bump MSTest.TestAdapter from 2.2.3 to 2.2.6

Bumps [MSTest.TestAdapter](https://github.com/microsoft/testfx) from 2.2.3 to 2.2.6.
- [Release notes](https://github.com/microsoft/testfx/releases)
- [Commits](microsoft/testfx@v2.2.3...v2.2.6)

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

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

tests/FluentEmail.Graph.Tests/FluentEmail.Graph.Tests.csproj

@@ -10,7 +10,7 @@
   <ItemGroup>
     <PackageReference Include="FluentAssertions" Version="5.10.3" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.4" />
-    <PackageReference Include="MSTest.TestAdapter" Version="2.2.3" />
+    <PackageReference Include="MSTest.TestAdapter" Version="2.2.6" />
     <PackageReference Include="MSTest.TestFramework" Version="2.2.3" />
     <PackageReference Include="coverlet.collector" Version="3.0.3">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>