pgsql: Doc: Update ulinks to RFC documents to avoid redirect

Doc: Update ulinks to RFC documents to avoid redirect

The tools.ietf.org site has been decommissioned and replaced by a
number of sites serving various purposes.  Links to RFCs and BCPs
are now 301 redirected to their new respective IETF sites.  Since
this serves no purpose and only adds network overhead, update our
links to the new locations.

Backpatch to all supported versions.

Discussion: https://postgr.es/m/3C1CEA99-FCED-447D-9858-5A579B4C6687@yesql.se
Backpatch-through: v12

Branch
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REL_16_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/f6dcddf3e851c00e877c5b4302a54e49e2775c44

Modified Files
--------------
doc/src/sgml/acronyms.sgml     |  2 +-
doc/src/sgml/catalogs.sgml     |  2 +-
doc/src/sgml/charset.sgml      |  4 ++--
doc/src/sgml/client-auth.sgml  | 16 ++++++++--------
doc/src/sgml/datatype.sgml     |  4 ++--
doc/src/sgml/ecpg.sgml         |  2 +-
doc/src/sgml/func.sgml         |  4 ++--
doc/src/sgml/json.sgml         |  2 +-
doc/src/sgml/libpq.sgml        |  8 ++++----
doc/src/sgml/pgcrypto.sgml     |  2 +-
doc/src/sgml/protocol.sgml     |  6 +++---
doc/src/sgml/ref/psql-ref.sgml |  2 +-
doc/src/sgml/textsearch.sgml   |  2 +-
doc/src/sgml/uuid-ossp.sgml    |  2 +-
14 files changed, 29 insertions(+), 29 deletions(-)