Widgets:
- Remove the !important styles that were overriding the widget width when expanded.
- Fix missing border-bottom from widgets when dragged and expanded.
Props shaunandrews, see #26117.
Built from https://develop.svn.wordpress.org/trunk@26275


git-svn-id: http://core.svn.wordpress.org/trunk@26180 1a063a9b-81f0-0310-95a4-ce76da25c4cd