doc: Remove superfluous bracket in synopsis
Commit
9c08aea6a30 accidentally added one too many end brackets
in the synopsis for CREATE DATABASE .. strategy = strat. Fix by
removing. Backpatch to v15 where it was introduced.
Reported-by: tim.needham2@gmail.com
Discussion: https://postgr.es/m/
170734160862.
3279712.
810853722572951776@wrigleys.postgresql.org
Backpatch-through: v15