We should remove the deprecated window.gM function (from jqueryMsg). It's been deprecated since basically ever (prior to rSVN105974) and logging warnings since MW 1.23 (aad0185da5269da7e059be9f1fabfb8b3ccffb87).
Search results in extensions:
Searching 90199 files for "gM" (case sensitive, whole word) extensions/Contest/resources/contest.special.contest.js: 57: alert( window.gM( 'contest-contest-reminder-failed', data.contestantcount ) ); extensions/EducationProgram/resources/ep.enlist.js: 262: this.$dialog.append( $( '<p>' ).text( gM( extensions/EducationProgram/resources/ep.js: 48: return gM.apply( this, arguments ); extensions/EducationProgram/resources/ep.pager.js: 220: alert( window.gM( 'ep-pager-delete-selected-fail', ids.length ) ); 4 matches across 4 files