Drop `third_party_ai_features_enabled` column

What does this MR do and why?

• Was ignored in 16.9: !142849 (merged)
• Next step is to drop in 16.10
• #439402 (closed)
• Will remove from ignore list in 16.11 per https://docs.gitlab.com/ee/development/database/avoiding_downtime_in_migrations.html#ignoring-the-column-release-m
• Updating remove_after for code_suggestions while I am here because that was added as an ignore as part of %16.10 so should be dropped in %16.11 and removed as ignore in %17.0

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

n/a just a DB column removal

How to set up and validate locally

n/a just a DB column removal