fix(rid): refetch's redo hint only for changed levels and deleted spikes

New hours are forecast by the catch-up anyway, and a forecast issued without
the discharge RID added later is still what was issued; only a corrected or
deleted level makes the issued forecasts wrong.

rust/README.md

@@ -25,7 +25,7 @@ ping-collector fill-gaps <days|all> # re-fetch RID reports with holes
 ping-collector refetch FROM [TO]    # re-fetch the RID reports of FROM..=TO (YYYY-MM-DD) even
                                     # without holes, through the spike screening: corrects
                                     # readings RID revised, deletes stored spikes; prints the
-                                    # catch-up-forecasts command when readings changed
+                                    # catch-up-forecasts command when stored levels changed
 ping-collector check-db             # connect, create missing tables, row counts
 ping-collector forecast [--json] [--save] [--now T] [--rain-file F]
                                     # forecast from the database and print it