delete_in_topic: Don't unnecessarily fetch .recipient.

This reverts commit f119c33789.
With 51cef01c29 merged, there is no need
to fetch .recipient here, as it won't be accessed by the delete messages
codepath.

zerver/views/streams.py

@@ -1323,10 +1323,8 @@ def delete_in_topic(
         if time.monotonic() >= start_time + 50:
             return json_success(request, data={"complete": False})
         with transaction.atomic(durable=True):
-            messages_to_delete = (
-                messages.select_related("recipient")
-                .order_by("-id")[0:batch_size]
-                .select_for_update(of=("self",))
+            messages_to_delete = messages.order_by("-id")[0:batch_size].select_for_update(
+                of=("self",)
             )
             if not messages_to_delete:
                 break