[16] ALTER SUBSCRIPTION ... SET (run_as_owner = ...) is a no-op

Repro:
  ALTER SUBSCRIPTION s1 SET (run_as_owner = true);
  SELECT subrunasowner FROM pg_subscription WHERE subname='s1';
   subrunasowner
  ---------------
   f
  (1 row)

It also looks like a change to that field may not cause the
subscription worker to restart. It would be good to add a test for that
case.

Regards,
    Jeff Davis