fix(uptime): do not null out subscription id when disabling a monitor (#97844)

Author: klochek

src/sentry/uptime/subscriptions/tasks.py

@@ -135,8 +135,6 @@ def delete_remote_uptime_subscription(uptime_subscription_id, **kwargs):
     subscription_id = subscription.subscription_id
     if subscription.status == UptimeSubscription.Status.DELETING.value:
         subscription.delete()
-    else:
-        subscription.update(subscription_id=None)
 
     if subscription_id is not None:
         for region_slug in region_slugs: