Ensure sitemap entries reflect opt-in set changes within the normal sitemap regeneration cadence.

Sitemaps on WMF wikis are regenerated on a schedule (typically daily or weekly) rather than on every content change, and this is both fine and correct for opted-in abstract articles too: a newly-activated opt-in becomes crawlable on the next regeneration, and a newly-deactivated opt-in drops out of the sitemap on the next regeneration. No bespoke invalidation path is needed — the normal sitemap cadence is the right granularity. This bullet commits to inheriting that cadence rather than building a separate faster-invalidation mechanism.