postgres_fdw: Fix whitespace violation in connection.c

postgres_fdw: Fix whitespace violation in connection.c

Previously a continuation line in the call to libpqsrv_connect_params_start()
in postgres_fdw/connection.c was indented with spaces, violating
the PostgreSQL project's whitespace rules for C files and triggering
git show --check.

This commit reformats the code to avoid that layout and use indentation
consistent with project style. No functional change.

Reported-by: Peter Eisentraut <peter@eisentraut.org>
Author: Chao Li <lic@highgo.com>
Author: Fujii Masao <masao.fujii@gmail.com>
Discussion: https://postgr.es/m/2620a664-7b44-48b2-9aa8-5f0131702d9c@eisentraut.org