wayland: Trigger full focus sync after keyboard focus surface is destroyed
This used to be implicitly done by popups using a META_GRAB_OP_WAYLAND_POPUP MetaDisplay grab. Since commit a8cd488c Wayland popups no longer do that, so the keyboard focus was simply unset if a popup was destroyed while having the keyboard focus.
Trigger a full input focus sync, so the correct MetaWaylandKeyboard focus surface is looked up from the focused MetaWindow.
Fixes: a8cd488c - wayland: Drop redundant MetaDisplay grab op