Bump Microsoft.AspNetCore.Mvc.Testing from 6.0.13 to 8.0.0

Bumps [Microsoft.AspNetCore.Mvc.Testing](https://github.com/dotnet/aspnetcore) from 6.0.13 to 8.0.0.
- [Release notes](https://github.com/dotnet/aspnetcore/releases)
- [Changelog](https://github.com/dotnet/aspnetcore/blob/main/docs/ReleasePlanning.md)
- [Commits](dotnet/aspnetcore@v6.0.13...v8.0.0)

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

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

Directory.Build.props

@@ -48,7 +48,7 @@
       <MicrosoftExtensionsLoggingConfiguration>6.0.0</MicrosoftExtensionsLoggingConfiguration>
       <BogusVersion>34.0.2</BogusVersion>
       <NullablePkg>1.3.0</NullablePkg>
-      <MicrosoftAspNetCoreMvcTestingVersion>6.0.13</MicrosoftAspNetCoreMvcTestingVersion>
+      <MicrosoftAspNetCoreMvcTestingVersion>8.0.0</MicrosoftAspNetCoreMvcTestingVersion>
       <AzureMessagingEventHubsVersion>5.7.3</AzureMessagingEventHubsVersion>
     </PropertyGroup>