Fix menu field height in Firefox. It's about 25px in all other browsers, so it should be the same here  as well for consistency.

git-svn-id: https://plugins.svn.wordpress.org/admin-menu-editor/trunk@955988 b8457f37-d9ea-0310-8a92-e5e31aec5664
Stable = 1.4

git-svn-id: https://plugins.svn.wordpress.org/admin-menu-editor/trunk@955989 b8457f37-d9ea-0310-8a92-e5e31aec5664