Remove, from stable branches, the new assertion of no pg_dump OID sort.

Commit 0decd5e89db9f5edb9b27351082f0d74aae7a9b6 recently added the
assertion to confirm dump order remains independent of OID values.  The
assertion remained reachable via DO_DEFAULT_ACL.  Given the release wrap
tomorrow, make the assertion master-only.

Reported-by: Alexander Lakhin <exclusion@gmail.com>
Reviewed-by: Robert Haas <robertmhaas@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/d32aaa8d-df7c-4f94-bcb3-4c85f02bea21@gmail.com
Backpatch-through: 13-18

src/bin/pg_dump/pg_dump_sort.c

@@ -447,7 +447,6 @@ DOTypeNameCompare(const void *p1, const void *p2)
 	 * consequence of the test using "pg_restore -j", which doesn't fully
 	 * constrain OID assignment order.
 	 */
-	Assert(false);
 	return oidcmp(obj1->catId.oid, obj2->catId.oid);
 }