icons: Give "Stop" a filled background, aligned with others in the pack
icons: Give "Stop" a filled background, aligned with others in the pack

Bug: T132991
Change-Id: Ia195bf844b9d55518ad6af3b888739fe87ba5a9f

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