pgsql: Skip RSA-PSS ssl test when using LibreSSL.

Skip RSA-PSS ssl test when using LibreSSL.

Presently, LibreSSL does not have working support for RSA-PSS,
so disable that test. Per discussion at
https://marc.info/?l=libressl&m=174664225002441&w=2
they do intend to fix this, but it's a ways off yet.

Reported-by: Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
Author: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Reviewed-by: Daniel Gustafsson <daniel(at)yesql(dot)se>
Discussion: https://postgr.es/m/CA+hUKG+fLqyweHqFSBcErueUVT0vDuSNWui-ySz3+d_APmq7dw@mail.gmail.com
Backpatch-through: 15

Branch
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REL_17_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/3007fee7f2924e76748e81d7fd86cdf24a98a520

Modified Files
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src/test/ssl/t/002_scram.pl | 6 ++++++
1 file changed, 6 insertions(+)