Synthetic damage sprites do not update upon repair.

### Testmerges

#4224 #4063 #4336 #4352 #4353 #4354 #4381

### Description of the bug

Synthetic damage sprites only update upon taking damage, repairing via any means (Smartpack, welder/cable coil or repair station) will not change the damage sprites to their previous state of undamaged, meaning that even a fully repaired synth will have their face half-submerged in synth-goop instead of being pristine.

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

Upon repair, the synthetic damage sprites should reset to the state where there is no damage, instead of not updating and only updating when taking damage (thus moving it to the least damage sprite version where theres only 1 pixel of synth goop on say, the face)

### How do we reproduce this bug?

1. Be a synthetic and take damage until damage sprites are visible.
2. Repair damage to region (head is the best for this, as its damaged states are the most obvious)
3. Notice that the region has not gone back to the repaired/full integrity state.

### 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)