manager: drop loop arg from stop event
manager: drop loop arg from stop event

Closes #1647

Looks like we can just drop this arg together, as it is completely unused
by the asyncio.Event() internals.

Signed-off-by: Tycho Andersen <6b523322678240882acbb4da5312a12d8cd0082d@tycho.ws>

qtile/qtile,ramnes/qtile,ramnes/qtile,qtile/qtile