Fix alarmed off state incorrectly setting _is_on to True

Remove `self._is_on = True` from alarmed/off/state.py __init__.
This line contradicted the IsOff mixin, which defines is_on as False.

The bug caused:
- KNX plugin to not send on/off commands during alarmed state toggles
  (both alarmed_on and alarmed_off incorrectly reported is_on=True)
- Zone lights to stop toggling when alarmed
- Lights to get stuck in forced_off after alarmed transitions

The state now correctly inherits is_on=False from the IsOff mixin,
allowing proper KNX command generation during toggle transitions.

Assisted-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: majamassarini

home/appliance/light/zone/state/alarmed/off/state.py

@@ -49,6 +49,5 @@ def __init__(self, events=None, events_disabled=None):
         self.alarmed_on = home.appliance.light.zone.state.alarmed.on.State
         self.forced_on = home.appliance.light.zone.state.forced.on.State
         self.forced_off = home.appliance.light.zone.state.forced.off.State
-        self._is_on = True
 
         super(State, self).__init__(events, events_disabled)