Remove inGroupWith field of quests in questieDB. The field is not used for anything, but it is still handled all in datastructures wasting cpu cycles and memory.

Example what it (has been) is for:
A player must complete quests A, B, C before D can be accepted. And A, B, C are not depending each other.
Now quest A has data: inGroupWith = B, C. B has data: inGroupWith = A, C. C has data: inGroupWith = A, B. These are not used for anything currently.
Instead Questie gets data from preQuestGroup field of quest D: preQuestGroup = A, B, C

Can't remove the field from auto-generated database files as those are used by 3rd party.

Not worth to do. Maybe, just maybe to remove from compressed database, but still better keep if there comes some use.