Remove unwated ref to datapoint API key

Author: wxtim

cylc/flow/etc/tutorial/cylc-forecasting-workflow/bin/get-observations

@@ -193,7 +193,7 @@ def main(site_id, api_key=None):
             site_id, dist = get_nearby_site(site_id, badsites)
 
     if obs is None:
-        print('No API key provided, falling back to archived data')
+        print('Obs unavailable, falling back to archived data')
         data = get_archived_data(site_id, cycle_point)
         obs = extract_observations(data)