[Jobs] Get rid of the mounting in file mounts translation

[Michaelvll]

We currently have translates the file mounts for managed jobs to submit to an intermediate bucket, and have it both copy and mounted to the remote worker for the job. We should get rid of the mounting part as that may not work on some systems that does not support mounting, e.g. GKE

Version & Commit info:

• sky -v: PLEASE_FILL_IN
• sky -c: PLEASE_FILL_IN