Remove unused and confusing IOC HIFIMAG from IOCs

As a developer, I don't want to be confused by having both HIFIMAG and HIFIMAGS in the IOC lists.

** Acceptance Criteria **
1. Only HIFIMAGS remains in the IOC list

** Notes **
1. Initially HIFIMAG was created to talk to the Cryogenic PSUs, as these could be used elsewhere the code to talk to them was eventually placed in CRYOSMS
2. Whilst that directory could have been reused as this relates to multiple magnets, not just a single magnet then the name HIFIMAGS is more descriptive