Clean up comments in scheduler_job_runner.py

Removed commented-out lines for clarity.

Author: shivaam

airflow-core/src/airflow/jobs/scheduler_job_runner.py

@@ -1981,15 +1981,7 @@ def _mark_backfills_complete(self, session: Session = NEW_SESSION) -> None:
         # todo: AIP-78 simplify this function to an update statement
         query = select(Backfill).where(
             Backfill.completed_at.is_(None),
-            # Guard: backfill must have at least one 
-          
-          
-          
-          
-          
-          
-          
-          association,
+            # Guard: backfill must have at least one association,
             # otherwise it is still being set up (see #61375).
             exists(select(BackfillDagRun.id).where(BackfillDagRun.backfill_id == Backfill.id)),
             ~exists(