pgsql: Update SELinux links in sepgsql documentation

Update SELinux links in sepgsql documentation

The SELinux FAQ and User Guide links has been redirecting from the
URL in our documentation for a very long time (since 2011 according
to archive.org) but the redirect is no longer maintained and they
now return a 404 since some time back. Fix by replacing the links
with the targets of the redirect.

This is a follow-up to commit cc1853b3 which updated the links in
version 10 through master, which albeit different from this one
were also yielding 404.

Discussion: https://postgr.es/m/AF6E0911-CA4A-4B5B-91AB-51E388674569@yesql.se

Branch
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REL9_6_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/6315261639e5a81d63082d39f715c2bd9a1bd43a

Modified Files
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doc/src/sgml/sepgsql.sgml | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)