Remove SCRIPT_DEBUG reference from register_admin_color_schemes().

Instead, script-loader.php handles converting .min.css to .css when SCRIPT_DEBUG is on, and has since r21592. (This was done for compatibility with plugin color schemes that used .css and .dev.css.)

see #25858.


git-svn-id: https://develop.svn.wordpress.org/trunk@26147 602fd350-edb4-49c9-b593-d223f7449a82