docs(jobs): state what stale_timeout=0 still cleans up

Review follow-up: the stale_timeout entry still said 0 skips the cleanup, but the success and error records of keys that have left both key_source and the target are now removed whatever the timeout. The test for records of existing rows covers a fresh record only, and its docstring now says so.

(cherry picked from commit 6a1e171)

Author: dimitri-yatsenko

src/datajoint/jobs.py

@@ -340,7 +340,9 @@ def refresh(
         stale_timeout : float, optional
             Seconds after which jobs are checked for staleness.
             Jobs older than this are removed if key not in key_source.
-            Default from ``config.jobs.stale_timeout``. Set to 0 to skip.
+            Default from ``config.jobs.stale_timeout``. Set to 0 to skip the
+            age-based check; the cleanup of success and error records whose
+            keys have left both key_source and the target runs regardless.
         orphan_timeout : float, optional
             Seconds after which reserved jobs are considered orphaned.
             Reserved jobs older than this are deleted and re-added as pending.

tests/integration/test_jobs_refresh.py

@@ -131,7 +131,7 @@ def test_refresh_removes_records_of_vanished_keys(pipeline):
 
 
 def test_refresh_keeps_success_records_of_existing_rows(schema_by_backend):
-    """A success record stays while its row exists, even if its key leaves key_source."""
+    """A fresh success record stays while its row exists, even if its key leaves key_source."""
 
     @schema_by_backend
     class Raw(dj.Manual):