Upgrade `mediaelement` to the latest version. Includes a variety of bug fixes made since the 4.2.6 release; see https://github.com/mediaelement/mediaelement/releases. Props danieliser, Hareesh Pillai. Fixes #46681. Built from https://develop.svn.wordpress.org/trunk@46436 git-svn-id: http://core.svn.wordpress.org/trunk@46234 1a063a9b-81f0-0310-95a4-ce76da25c4cd