Fix comment in libpqrcv_check_conninfo().
Previously, the comment incorrectly stated that libpqrcv_check_conninfo()
returns true or false based on the connection string check.
However, this function actually has a void return type and
raises an error if the check fails.
Author: Rintaro Ikeda
Reviewed-by: Jelte Fennema-Nio, Fujii Masao
Discussion: https://postgr.es/m/
6a1ca81b27fec4da0ccdfaaaec787982@oss.nttdata.com