pgsql: Remove read-only server settings lc_collate and lc_ctype

Remove read-only server settings lc_collate and lc_ctype

The GUC settings lc_collate and lc_ctype are from a time when those
locale settings were cluster-global. When those locale settings were
made per-database (PG 8.4), the settings were kept as read-only. As
of PG 15, you can use ICU as the per-database locale provider, so
examining these settings is already less meaningful and possibly
confusing, since you need to look into pg_database to find out what is
really happening, and they would likely become fully obsolete in the
future anyway.

Reviewed-by: Jeff Davis <pgsql(at)j-davis(dot)com>
Discussion: https://www.postgresql.org/message-id/696054d1-bc88-b6ab-129a-18b8bce6a6f0@enterprisedb.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/b0f6c437160db640d4ea3e49398ebc3ba39d1982

Modified Files
--------------
contrib/citext/expected/citext_utf8.out | 4 +--
contrib/citext/expected/citext_utf8_1.out | 4 +--
contrib/citext/sql/citext_utf8.sql | 4 +--
doc/src/sgml/config.sgml | 32 ----------------------
src/backend/utils/init/postinit.c | 4 ---
src/backend/utils/misc/guc_tables.c | 26 ------------------
src/test/regress/expected/collate.icu.utf8.out | 4 +--
src/test/regress/expected/collate.linux.utf8.out | 6 ++--
.../regress/expected/collate.windows.win1252.out | 6 ++--
src/test/regress/sql/collate.icu.utf8.sql | 4 +--
src/test/regress/sql/collate.linux.utf8.sql | 6 ++--
src/test/regress/sql/collate.windows.win1252.sql | 6 ++--
12 files changed, 22 insertions(+), 84 deletions(-)