This came up in T126861 where we identified this as desired
behavior.
Change-Id: I37e8f59b4b88cc289709da9802df3a0f123939b1
'APIEditBeforeSave': Before saving a page with api.php?action=edit, after
processing request parameters. Return false to let the request fail, returning
an error message or an <edit result="Failure"> tag if $resultArr was filled.
+Unlike for example 'EditFilterMergedContent' this also being run on undo.
$editPage: the EditPage object
$text: the new text of the article (has yet to be saved)
&$resultArr: data in this array will be added to the API result