Using percentages for playlist font-sizing was ambitious, but fell prey to `editor-style.css` in the admin. We have switched to using pixels. The editor styles were also forcing MediaElement players to inherit `font-family`, which was undesirable. And while we're at it, remove the top and bottom border from the playlist's list of tracks, which adds a dash of lovely to the playlist's default styles.

Props nacin for the addition of `&mdash;` in the playlist track list.
Fixes #27600.


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git-svn-id: http://core.svn.wordpress.org/trunk@27696 1a063a9b-81f0-0310-95a4-ce76da25c4cd
Use correct formatting function. see [27864], see #27574.

Built from https://develop.svn.wordpress.org/trunk@27866


git-svn-id: http://core.svn.wordpress.org/trunk@27697 1a063a9b-81f0-0310-95a4-ce76da25c4cd