Mobs are supposed to despawn in minimum 600 ticks in pitch black rooms. 
If the room is lit, then they should despawn 3 times faster, so in 200 ticks.

The issue I have here, is I have a Witch Hut farm, that is completely pitch black (lights levels of 0 everywhere) and witches are despawning after 200 GT.

I believe the issue is caused by  Raider#updateNoActionTime which always add +2 to the `noActionTime` variable, regardless of if the mob is in a raid or not. I believe it is missing a `if this.getCurrentRaid() != null` before incrementing the noActionTime and should default to `super` (which should hopefully delegate to Monster#updateNoActionTime, restoring the light level dependent behavior).

This also means that other Illagers not spawned as part of a raid (but still inherit the Raider trait) will despawn faster than normal, so Pillager Tower Pillagers also despawn faster than they should.