fix: correct API endpoint in get_training_plan_by_id

Author: PELLEGATTA FEDERICO

garminconnect/__init__.py

@@ -2298,7 +2298,7 @@ def get_training_plan_by_id(self, plan_id: int | str) -> dict[str, Any]:
 
         plan_id = _validate_positive_integer(int(plan_id), "plan_id")
 
-        url = f"{self.garmin_connect_training_plan_url}/plans/{plan_id}"
+        url = f"{self.garmin_connect_training_plan_url}/phased/{plan_id}"
         logger.debug("Requesting training plan details for %s", plan_id)
         return self.connectapi(url)