There are several ways to this and it also depends on the storage you are using but the easiest is to simply remove it from the old job and add it to the new job. Once the old job runs again it will tell you this VM is no longer being processed and to ensure that this was intentional, which is normal. The VM that was removed will be moved down to Disk (Imported) under backups as its no longer being processed by that job. You can still restore from this as normal and when you are ready to remove it just right click and remove from disk.
If you want it to auto fall off and get removed from the disk after a certain retention after you delete it, before you delete the VM, In the settings of the job go to Storage-----Advanced--------Maintenance tab --------Full Backup file maintenance. Click the remove deleted VM data after blah and choose how many days retention. This should work but I never used it and normally just remove them on my own.
The only downside to removing from old and adding to new is that it will need to run a active full on the new job.