GtkMenuTracker: one more visibility tweak

GtkMenuTracker: one more visibility tweak

On creation, we call action_removed() in case the action was missing
from the start.  Because we just created the action, 'can_activate' will
always be FALSE here and this function will therefore always do nothing.

We do want the visibility state to be updated though, for the case where
the action is missing but the item should still be visible from the
start.

Update the visibility directly instead of trying to call
action_removed().

https://bugzilla.gnome.org/show_bug.cgi?id=735122