Calls for the removal of Sajax go back to (at least) October of 2012, when it
was already possible to describe the library as "ancient". The work to mark
the library as deprecated and to update its callers in Core was completed
by Alex Monk two years ago. Usage in extensions was removed long ago in most
cases, and the last holdout -- SecurePoll -- was migrated by Frances Hocutt
last month. There is a long tail of usage in the MediaWiki namespace, but it
should not block this patch.