Remove the UI for setting the default width and height for embeds. Width was confusing as it
was blank by default (inheriting the content width from the theme, or 500px). The height is
now calculated as 1.5x the content width, or 1000px, whichever is smaller.
The [embed] shortcode can still receive manual height and width attributes. This just removes
the global settings.
props wonderboymusic. see #21719.
git-svn-id: https://develop.svn.wordpress.org/trunk@21998 602fd350-edb4-49c9-b593-d223f7449a82