Fix MediaElement i18n.

props Namibia, eherman24.
fixes #28366 for trunk.
Built from https://develop.svn.wordpress.org/trunk@28801


git-svn-id: http://core.svn.wordpress.org/trunk@28610 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Revert [28776] and use a correct variable instead.

props miqrogroove.
fixes #28575.
Built from https://develop.svn.wordpress.org/trunk@28802


git-svn-id: http://core.svn.wordpress.org/trunk@28611 1a063a9b-81f0-0310-95a4-ce76da25c4cd