Squad Leaders lose Leader access

### Testmerges

N/A

### Round ID

N/A

### Description of the bug
Actual SLs lose ACCESS_MARINE_LEADER
Presumably on switching aSLs around?
Squad Transfers might also be involved.

Needs reproducing, unsure of the exact steps at the moment.

Has happened whilst the Leader isn't the SL/aSL
And when they are.

### What's the difference with what should have happened?

They shouldn't lose access they already should have by nature of their position.

### How do we reproduce this bug?

1. Good question.
2.
3.
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### Issue Bingo

- [x] Issue could be reproduced at least once
- [x] Issue happened in a recent (less than 7 days ago) round
- [x] Couldn't find an existing issue about this (https://github.com/cmss13-devs/cmss13/issues)