doc: Remove superfluous bracket in synopsis

Commit 9c08aea 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

Author: danielgustafsson

doc/src/sgml/ref/create_database.sgml

@@ -25,7 +25,7 @@ CREATE DATABASE <replaceable class="parameter">name</replaceable>
     [ WITH ] [ OWNER [=] <replaceable class="parameter">user_name</replaceable> ]
            [ TEMPLATE [=] <replaceable class="parameter">template</replaceable> ]
            [ ENCODING [=] <replaceable class="parameter">encoding</replaceable> ]
-           [ STRATEGY [=] <replaceable class="parameter">strategy</replaceable> ] ]
+           [ STRATEGY [=] <replaceable class="parameter">strategy</replaceable> ]
            [ LOCALE [=] <replaceable class="parameter">locale</replaceable> ]
            [ LC_COLLATE [=] <replaceable class="parameter">lc_collate</replaceable> ]
            [ LC_CTYPE [=] <replaceable class="parameter">lc_ctype</replaceable> ]