fix TimeAlarm signature

shared-bindings/alarm/time/TimeAlarm.c

@@ -45,7 +45,7 @@ mp_obj_t MP_WEAK rtc_get_time_source_time(void) {
 //|     """Trigger an alarm when the specified time is reached."""
 //|
 //|     def __init__(
-//|         self, monotonic_time: Optional[float] = None, epoch_time: Optional[int] = None
+//|         self, *, monotonic_time: Optional[float] = None, epoch_time: Optional[int] = None
 //|     ) -> None:
 //|         """Create an alarm that will be triggered when `time.monotonic()` would equal
 //|         ``monotonic_time``, or when `time.time()` would equal ``epoch_time``.