Deploy changes from https://phabricator.wikimedia.org/T87336 to all projects
Do not deploy prior to Dec 8. Test thoroughly on beta cluster to account for any possible bugs.
[x] `$wgPageImagesLeadSectionOnly` should be set to true on beta cluster to allow testing for possible bugs
[x] Verify we are okay with the beta cluster behaviour (Olga)
[] `$wgPageImagesLeadSectionOnly` should be set to true in production (initially to a single large wiki to avoid fallout).
[] Wait 1-2 days to get a sense of impact on cawiki before setting`$wgPageImagesLeadSectionOnly` to true in production for all wikis. Remember that only newly edited pages will get updated with new page images.
[] After this happens images returned by pageimages will only come from the lead section of an article. When enabling be sure to check error logs, performance graphs and end results.
[] The change when merged should be announced on wikitech-l and mediawiki-api (or mediawiki-api-announce) (Olga)
[] Upon sign off a card should be created to remove the `$wgPageImagesLeadSectionOnly` config variable from the Page Images extension and make this the default behaviour of the extension.