bankruptcy: Remove broken push notifications loop.

The loop I added here in 5b49839b08 was
ill-conceived.  The critical issue was that despite its name,
do_clear_mobile_push_notifications_for_ids does not immediately clear
push notifications (Except in our test suite, where `send_event`
immediately calls into the queue worker code!).

Instead, it queues work to clear those push notifications.  Which
means that the first user to declare bankruptcy with a large number of
unreads will fill the queue, and then this will just be an infinite
loop adding more work to the queue.

zerver/lib/actions.py

@@ -4078,16 +4078,11 @@ def do_mark_all_as_read(user_profile: UserProfile, client: Client) -> int:
 
     # First, we clear mobile push notifications.  This is safer in the
     # event that the below logic times out and we're killed.
-    while True:
     all_push_message_ids = UserMessage.objects.filter(
         user_profile=user_profile,
     ).extra(
         where=[UserMessage.where_active_push_notification()],
     ).values_list("message_id", flat=True)[0:10000]
-
-        if len(all_push_message_ids) == 0:
-            break
-
     do_clear_mobile_push_notifications_for_ids(user_profile, all_push_message_ids)
 
     msgs = UserMessage.objects.filter(