Possibly incomplete list of things to clean up:
- Default $wgStructuredChangeFiltersShowPreference to true, and/or deprecate it, and/or remove it
- Same for $wgStructuredChangeFiltersShowWatchlistPreference
- Same for $wgStructuredChangeFiltersOnWatchlist
- Remove beta feature code in WikimediaMessages, including $wgEnableRcFiltersBetaFeature
- Remove the RcFiltersInvite guided tour in WikimediaMessages