Since this extension uses extension.json, it already requires 1.25+ so
no need to keep the old code around.
Change-Id: I6f968be3b7ef7cbc7193c8e103beb36ecf9c7b60
MediaWiki core change I04b1a384 added support for i18n of API module
help. This takes advantage of that while still maintaining backwards
compatibility with earlier versions of MediaWiki.
Once support for MediaWiki before 1.25 is dropped, the methods marked
deprecated in this patch may be removed.
Change-Id: I67395aff48185f3e09da31b51a08aa2541fe6a17