Bump Microsoft.AspNetCore.Mvc.Testing from 6.0.8 to 6.0.9 in /src

Bumps [Microsoft.AspNetCore.Mvc.Testing](https://github.com/dotnet/aspnetcore) from 6.0.8 to 6.0.9.
- [Release notes](https://github.com/dotnet/aspnetcore/releases)
- [Changelog](https://github.com/dotnet/aspnetcore/blob/main/docs/ReleasePlanning.md)
- [Commits](dotnet/aspnetcore@v6.0.8...v6.0.9)

---
updated-dependencies:
- dependency-name: Microsoft.AspNetCore.Mvc.Testing
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

src/AzureIoTHub.Portal.Tests.Unit/AzureIoTHub.Portal.Tests.Unit.csproj

@@ -22,7 +22,7 @@
     <PackageReference Include="bunit.web.testcomponents" Version="1.9.8" />
     <PackageReference Include="Docker.DotNet" Version="3.125.11" />
     <PackageReference Include="FluentAssertions" Version="6.7.0" />
-    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="6.0.8" />
+    <PackageReference Include="Microsoft.AspNetCore.Mvc.Testing" Version="6.0.9" />
     <PackageReference Include="Microsoft.CodeAnalysis.Analyzers" Version="3.3.3">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>