Make psql DETAIL line test unconditionally optional.

Make psql DETAIL line test unconditionally optional.

Commit 3e2a1496bae6 made the psql TAP test require the DETAIL line on
platforms with SA_SIGINFO, rather than making it optional. This
unexpectedly blew up on OpenBSD buildfarm members, because OpenBSD does
not set si_pid for SIGTERM signals even though it has SA_SIGINFO
defined.

So revert to the test as it was in commit 55890a919454, where the detail
line being missing never causes an error.

Author: Jakub Wartak <jakub.wartak@enterprisedb.com>
Suggested-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://www.postgresql.org/message-id/2007157.1776269052%40sss.pgh.pa.us