Return native timestamps for home connect (home-assistant#61116)

Author: balloob

homeassistant/components/home_connect/sensor.py

@@ -63,16 +63,14 @@ async def async_update(self):
                 elif (
                     self._state is not None
                     and self._sign == 1
-                    and dt_util.parse_datetime(self._state) < dt_util.utcnow()
+                    and self._state < dt_util.utcnow()
                 ):
                     # if the date is supposed to be in the future but we're
                     # already past it, set state to None.
                     self._state = None
                 else:
                     seconds = self._sign * float(status[self._key][ATTR_VALUE])
-                    self._state = (
-                        dt_util.utcnow() + timedelta(seconds=seconds)
-                    ).isoformat()
+                    self._state = dt_util.utcnow() + timedelta(seconds=seconds)
             else:
                 self._state = status[self._key].get(ATTR_VALUE)
                 if self._key == BSH_OPERATION_STATE: