After structured mentor list gets deployed (T310905), we should clean up a couple of things up:
- Remove code supporting wikitext-based mentor lists
- Remove GEMentorProvider and review&fix checks based on the variable
- Delete MentorWeightManager service
- Delete MentorProviderWikitext service
- Rewrite GrowthExperimentsMentorProvider service wiring to only return $geServices->getMentorProviderStructured()
- Remove config variables from operations/mediawiki-config