Fix misuse of pg_log_info() for details/hints.

Fix misuse of pg_log_info() for details/hints.

Two places in pg_dump_sort.c were using pg_log_info() to add
more details to a message printed with pg_log_warning().
This is bad, because at default verbosity level we would
print the warning line but not the details.  One should use
pg_log_warning_detail() or pg_log_warning_hint() instead.
Commit 9a374b77f got rid of most such abuses, but unaccountably
missed these.

Noted while studying a bug report from Sami Imseih.
Back-patch to v15 where 9a374b77f came in.  (Prior versions
don't have the missing-details misbehavior, for reasons
I didn't bother to track down.)

Discussion: https://postgr.es/m/2C1933AB-C2F8-499B-9D18-4AC1882256A0@amazon.com