[Magiclysm] Tweak spellcasting proficiency trigger

[rty275]

Summary

None

Purpose of change

1. Closes [Magiclysm] Spellcasting proficiency EOCs run for every single spell #72428 in combination with [Magiclysm] Fix spellcasting proficiency setup triggers #72473
2. With [Magiclysm] Fix spellcasting proficiency setup triggers #72473, the EOCs were correctly triggered by spell effects now, but still had the EVENT trigger of spellcasting_finish and were still triggering on every spell and now even throwing an error about having to use an ACTIVATION EOC. This fixes that.

Describe the solution

Change EVENT to ACTIVATION and delete the "spellcasting_finish" required_event

Describe alternatives you've considered

Continue letting errors happen?

Testing

Tested spellcasting, you only learn the correct proficiencies for each spell now, and no magiclysm proficiencies for spells from other mods. No more errors on spellcasting.

Additional context

Incredible thanks to @MNG-cataclysm for figuring out how to make the EOCs only trigger from their category of spells, that was definitely a bugfix beyond my own skills. I'm just glad to be able to tidy up some small errors.

Edit: Sorry about the weirdness in formatting for the purpose, I'm trying to figure out how to make the summary labeler not angry with me.