Remove duplicated `outline` property
Remove duplicated `outline` property

Removing duplicated `outline` property, which is already set in
`.theme-oo-ui-buttonElement ()`.

Change-Id: I47f72f2d6f94f4fb9270b40cbfd901b7b9403060

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