state: fix updating reaction count in reaction remove event

[Juby210]

No description provided.

[diamondburned]

What case does this fix cover? You should add a comment documenting such cases.

[Juby210]

What case does this fix cover? You should add a comment documenting such cases.

You are incrementing reaction count in add event, but you don't decrement it in remove event.
I have starboard bot and you could just increment star count by deleting reaction and adding it again.

Current code only decrements count if bot user removes reaction:

[diamondburned]

Wouldn't that mean the actual fix would be to omit the r.Me branch completely and keep the default: branch?

The r.Me check can just be its own if outside the switch case.