New admin styling: Disabled select boxes are not distinguishable

[TobiasBg]

Similarly to #26004 (which deals with checkboxes and radio buttons), disabled HTML <select disabled> boxes can not be distinguished from non-disabled ones.

There is ​CSS for select[disabled] in wp-admin.css to give it a lighter color, but that's again overridden by a more specific ​selector .wp-admin select.

Caused by [26293].

There's also a duplicate color property set for select. The attached patch fixes this.

[TobiasBg]

Fix color of disabled select boxes

[iammattthomas]

In 26733:

Ensure that disabled select elements are distinguishable from normal ones. Fixes #26456, props TobiasBg.