Bump Microsoft.NET.Test.Sdk from 16.8.3 to 16.9.1 in /src

Bumps [Microsoft.NET.Test.Sdk](https://github.com/microsoft/vstest) from 16.8.3 to 16.9.1.
- [Release notes](https://github.com/microsoft/vstest/releases)
- [Commits](microsoft/vstest@v16.8.3...v16.9.1)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

src/Cake.Issues.PullRequests.GitHubActions.Tests/Cake.Issues.PullRequests.GitHubActions.Tests.csproj

@@ -15,7 +15,7 @@
 
   <ItemGroup>
     <PackageReference Include="Cake.Issues.Testing" Version="1.0.0-beta0001" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.8.3" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.1" />
     <PackageReference Include="Cake.Core" Version="1.0.0" />
     <PackageReference Include="Cake.Testing" Version="1.0.0" />
     <PackageReference Include="Shouldly" Version="4.0.3" />