This reverts commit bab4d43206.
Reason for revert: breaks stated, advertised LTS compatibility that end-users expect (see https://www.mediawiki.org/wiki/Social_tools/MediaWiki_compatibility) (well, technically AJAXPoll isn't really a social tool per se, but some listings include it anyway, so...)
Change-Id: Ib0c4bde7040cdbb893acb200aa053fb1280078ff
MediaWiki has never used this path for running the maintenance
scripts, only the class name provided in the other parameter.
Providing the parameter is no longer needed in MediaWiki 1.43.
Also, remove outdated pitfall warning, it was fixed by marking
the method as protected in MediaWiki 1.35 (Ie73e6143bb).
Bug: T367918
Change-Id: I1818cf882e820bca9d7ec22b9bd30a86b81970f5