Remove use of WikiManager (T12716) #924

Job	Run time
call-mediawiki-tests-workflow (master, 8.1, 81, false, true) / master \| PHP 8.1	2m 7s
call-mediawiki-tests-workflow (REL1_42, 8.1, 81, true, false) / REL1_42 \| PHP 8.1	1m 51s
notify-irc	25s
	4m 23s

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