Improve documentation on DETACH PARTITION lock levels
This was forgotten in
71f4c8c6f74b.
Reported-by: Pavel Luzanov <p.luzanov@postgrespro.ru>
Author: Amit Langote <amitlangote09@gmail.com>
Discussion: https://postgr.es/m/
0688e7c3-8bc8-a3e4-9d8e-
3bcbbf3e1f4d@postgrespro.ru