Enable dotnet/format in unified-build (#18773)

Author: ViktorHofer

src/SourceBuild/content/repo-projects/Directory.Build.targets

@@ -738,7 +738,6 @@
       <TransitiveRepositoryReference Remove="msbuild" />
       <TransitiveRepositoryReference Remove="aspnetcore" />
       <TransitiveRepositoryReference Remove="razor" />
-      <TransitiveRepositoryReference Remove="format" />
       <TransitiveRepositoryReference Remove="nuget-client" />
       <TransitiveRepositoryReference Remove="fsharp" />
       <TransitiveRepositoryReference Remove="vstest" />