As far as I know there isn’t any automated way of removing user profiles from the job scheduler. If there was – how would it work?
The user profile associated with the job schedule entry may be necessary to grant certain authorities for the scheduled job. If the user profile is removed, and you change the scheduled job to use another profile, your job may no longer work correctly. I think this is something that will almost always need manual intervention to check that the scheduling is correctly assigned to another profile.