Remove unnecessary CSS rules on disabled buttons
Remove unnecessary CSS rules on disabled buttons

Removing unnecessary CSS rules on disabled buttons, it's already covered
by rules above.

Change-Id: I7972f62ac99fc97cdd6f6a4774c6bcc30d191b1d

wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui,wikimedia/oojs-ui