pgsql: Doc: update or remove dead external links.

Doc: update or remove dead external links.

Re-point comp.ai.genetic FAQ link to a more stable address.

Remove stale links to AIX documentation; we don't really need to
tell AIX users how to use their systems.

Remove stale links to HP documentation about SSL.  We've had to
update those twice before, making it increasingly obvious that
HP does not intend them to be stable landing points.  They're
not particularly authoritative, either.  (This change effectively
reverts bbd3bdba3.)

Daniel Gustafsson and Álvaro Herrera, per a gripe from
Kyotaro Horiguchi.  Back-patch, since these links are
just as dead in the back branches.

Discussion: https://postgr.es/m/20200709.161226.204639179120026914.horikyota.ntt@gmail.com

Branch
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REL_12_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/a5f18e8c2180ccfff07380efe52f93e9491dd9b5

Modified Files
--------------
doc/src/sgml/geqo.sgml         |  2 +-
doc/src/sgml/installation.sgml | 56 ------------------------------------------
doc/src/sgml/libpq.sgml        |  3 ---
doc/src/sgml/runtime.sgml      |  3 ---
4 files changed, 1 insertion(+), 63 deletions(-)