Bump MSTest.TestAdapter in /csharp/unit-testing/MSTest.Project (#4436)

Bumps [MSTest.TestAdapter](https://github.com/microsoft/testfx) from 2.2.1 to 2.2.3.
- [Release notes](https://github.com/microsoft/testfx/releases)
- [Commits](microsoft/testfx@v2.2.1...v2.2.3)

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

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

Author: dependabot[bot]

csharp/unit-testing/MSTest.Project/MSTest.Project.csproj

@@ -8,7 +8,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.1" />
-    <PackageReference Include="MSTest.TestAdapter" Version="2.2.1" />
+    <PackageReference Include="MSTest.TestAdapter" Version="2.2.3" />
     <PackageReference Include="MSTest.TestFramework" Version="2.2.1" />
     <PackageReference Include="coverlet.collector" Version="3.0.3">
       <PrivateAssets>all</PrivateAssets>