pgsql: Update pg_hba.conf example to reflect MD5 deprecation

Update pg_hba.conf example to reflect MD5 deprecation

In the wake of commit db6a4a985, remove most use of 'md5' from the
example configuration file. The only remainder is an example exception
for a client that doesn't support SCRAM.

Author: Mikael Gustavsson <mikael(dot)gustavsson(at)smhi(dot)se>
Reviewed-by: Peter Eisentraut <peter(at)eisentraut(dot)org>
Reviewed-by: Daniel Gustafsson <daniel(at)yesql(dot)se>
Reviewed-by: Andreas Karlsson <andreas(at)proxel(dot)se>
Reviewed-by: Laurenz Albe <laurenz(dot)albe(at)cybertec(dot)at>
Discussion: https://postgr.es/m/176595607507.978865.11597773194269211255@wrigleys.postgresql.org
Discussion: https://postgr.es/m/4ed268473fdb4cf9b0eced6c8019d353@smhi.se
Backpatch-through: 18

Branch
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REL_18_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/cf8c8adfe38138930569eeeae7d600cf465ef334

Modified Files
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doc/src/sgml/client-auth.sgml | 12 ++++++------
1 file changed, 6 insertions(+), 6 deletions(-)