applets/taskmanager: improve non-default grouped Meta+[number] UX
Clicking a grouped task respects your user preference with regards to behavior (it's configurable). However, when activating a grouped task using Meta+[number key], the only behavior that really makes sense is cycling between windows; all other behaviors are quite mouse-driven, and since you already had your fingers on the keyboard, using a mouse-driven UI here doesn't make much sense.
Accordingly, always use the cycling behavior when activating a grouped task with Meta+[number key].
BUG: 496208 FIXED-IN: 6.3.0