pgsql: pg_dumpall: simplify coding of dropDBs()

pg_dumpall: simplify coding of dropDBs()

There's no need for a StringInfo when all you want is a string
being constructed in a single pass.

Author: Álvaro Herrera <alvherre@kurilemu.de>
Reported-by: Ranier Vilela <ranier.vf@gmail.com>
Reviewed-by: Yang Yuanzhuo <1197620467@qq.com>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Andrew Dunstan <andrew@dunslane.net>
Discussion: https://postgr.es/m/CAEudQAq2wyXZRdsh+wVHcOrungPU+_aQeQU12wbcgrmE0bQovA@mail.gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/a198c26dede50a1fd4c22fb134b53ce8d4f8f5e3

Modified Files
--------------
src/bin/pg_dump/pg_dumpall.c | 17 +++++++----------
1 file changed, 7 insertions(+), 10 deletions(-)