rMW2c74b043568e removed some legacy hooks, and as a side-effect removed the output of the MediaWiki:Clearyourcache message, which was useful hint for new users to tell them how to clear their cache to get their changes to apply. Fortunately, they didn't remove any of the actual messages or styling, so restoring the message output shouldn't be difficult. Should be just a matter of putting this code back somewhere appropriate:
$dir = $this->getContext()->getLanguage()->getDir(); $lang = $this->getContext()->getLanguage()->getHtmlCode(); $outputPage->wrapWikiMsg( "<div id='mw-clearyourcache' lang='$lang' dir='$dir' class='mw-content-$dir'>\n$1\n</div>", 'clearyourcache' );