breezestyle: Remove extra margin for InstantPopup

Assigning a menu with instant popup mode to an action gives it
excessive left padding. Removing the extra margin fixes it.

BUG: 447288
2 jobs for !169 with work/fusionfuture/BUG447288-gwenview-open-with in 1 minute and 32 seconds (queued for 1 second)
latest merge request