Update CONTRIBUTING.MD
Update CONTRIBUTING.MD

Contributing guidelines for this repository reference an obsolete Templates repository.

Instead, potentially suggesting links to appropriate ASP.NET Core template repository.
aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore