Bump Microsoft.AspNetCore.Mvc.Testing and System.Text.Json

Bumps [Microsoft.AspNetCore.Mvc.Testing](https://github.com/dotnet/aspnetcore) and System.Text.Json. These dependencies needed to be updated together.

Updates `Microsoft.AspNetCore.Mvc.Testing` from 8.0.7 to 8.0.8
- [Release notes](https://github.com/dotnet/aspnetcore/releases)
- [Changelog](https://github.com/dotnet/aspnetcore/blob/main/docs/ReleasePlanning.md)
- [Commits](dotnet/aspnetcore@v8.0.7...v8.0.8)

Updates `System.Text.Json` from 8.0.0 to 8.0.4

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

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

Directory.Packages.props

@@ -57,7 +57,7 @@
     <PackageVersion Include="Swashbuckle.AspNetCore.SwaggerUI" Version="6.7.1" />
     <PackageVersion Include="Swashbuckle.AspNetCore.Annotations" Version="6.7.1" />
     <!-- Test -->
-    <PackageVersion Include="Microsoft.AspNetCore.Mvc.Testing" Version="8.0.7" />
+    <PackageVersion Include="Microsoft.AspNetCore.Mvc.Testing" Version="8.0.8" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
     <PackageVersion Include="xunit" Version="2.9.0" />
     <PackageVersion Include="xunit.runner.visualstudio" Version="2.8.1">