Minimum heights for the media modal to prevent it from scrunching up on tiny...

Minimum heights for the media modal to prevent it from scrunching up on tiny devices. (Panning is better.) props helenyhou. fixes #22747.



git-svn-id: https://core.svn.wordpress.org/trunk@23052 1a063a9b-81f0-0310-95a4-ce76da25c4cd