RemoteProjectName should be removed

[jordanstephens]

[Coderabbit suggested this issue in https://github.com//pull/1914#discussion_r2790137420_

This isn't really an urgent issue considering that the "too many projects error" is only returned by playground, and playground has its own implementation of RemoteProjectName, but this function is potentially reachable if the project name is not available from the loader, or in the flagset. It is confusing in that it returns the first project out of a seemingly unsorted list retrieved from the cd s3 bucket. This function has been marked deprecated for the base byoc client for a while now, so perhaps it's not a bad time to pull it out.