fix: make _notification_handler a normal function

Nothing is being awaited here and by making it a coro, each
notification has to spawn a new task which has to wait one
iteration of the event loop and increases latancy

src/bonaparte/device.py

@@ -276,7 +276,7 @@ def _validate_message(self, message: bytes | bytearray) -> None:
             msg = f"Invalid fooer {message[-1]}. Message should end with {FOOTER}."
             raise EfireMessageValueError(msg)
 
-    async def _notification_handler(
+    def _notification_handler(
         self, _char: BleakGATTCharacteristic, message: bytearray
     ) -> None:
         _LOGGER.debug(