Gracefully slide down the "{Name} is editing" notice portion of the post row, so everything isn't shifting down in an instant and throwing off people's clicks.

fixes #24553. props kadamwhite, johnbillion.

git-svn-id: https://core.svn.wordpress.org/trunk@24576 1a063a9b-81f0-0310-95a4-ce76da25c4cd