Improve trigger assign_unassigned by merging alive_triggerer_ids and …

…get_sorted_triggers queries

airflow/models/trigger.py

@@ -261,13 +261,11 @@ def assign_unassigned(
         if capacity <= 0:
             return
 
-        alive_triggerer_ids = session.scalars(
-            select(Job.id).where(
-                Job.end_date.is_(None),
-                Job.latest_heartbeat > timezone.utcnow() - datetime.timedelta(seconds=health_check_threshold),
-                Job.job_type == "TriggererJob",
-            )
-        ).all()
+        alive_triggerer_ids = select(Job.id).where(
+            Job.end_date.is_(None),
+            Job.latest_heartbeat > timezone.utcnow() - datetime.timedelta(seconds=health_check_threshold),
+            Job.job_type == "TriggererJob",
+        )
 
         # Find triggers who do NOT have an alive triggerer_id, and then assign
         # up to `capacity` of those to us.