pgsql: Remove pg_collation.collversion.

Remove pg_collation.collversion.

This model couldn't be extended to cover the default collation, and
didn't have any information about the affected database objects when the
version changed. Remove, in preparation for a follow-up commit that
will add a new mechanism.

Author: Thomas Munro <thomas(dot)munro(at)gmail(dot)com>
Reviewed-by: Julien Rouhaud <rjuju123(at)gmail(dot)com>
Reviewed-by: Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>
Discussion: https://postgr.es/m/CAEepm%3D0uEQCpfq_%2BLYFBdArCe4Ot98t1aR4eYiYTe%3DyavQygiQ%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/7d1297df0830725d4434ba7dbf71a9e8221ad49e

Modified Files
--------------
doc/src/sgml/catalogs.sgml | 11 ---
doc/src/sgml/func.sgml | 6 +-
doc/src/sgml/ref/alter_collation.sgml | 63 -----------------
doc/src/sgml/ref/create_collation.sgml | 21 ------
src/backend/catalog/pg_collation.c | 5 --
src/backend/commands/collationcmds.c | 88 ------------------------
src/backend/nodes/copyfuncs.c | 13 ----
src/backend/nodes/equalfuncs.c | 11 ---
src/backend/parser/gram.y | 18 +----
src/backend/tcop/utility.c | 12 ----
src/backend/utils/adt/pg_locale.c | 37 ----------
src/bin/pg_dump/pg_dump.c | 24 +------
src/include/catalog/catversion.h | 2 +-
src/include/catalog/pg_collation.dat | 7 +-
src/include/catalog/pg_collation.h | 5 --
src/include/catalog/toasting.h | 1 -
src/include/commands/collationcmds.h | 1 -
src/include/nodes/parsenodes.h | 11 ---
src/test/regress/expected/collate.icu.utf8.out | 3 -
src/test/regress/expected/collate.linux.utf8.out | 3 -
src/test/regress/sql/collate.icu.utf8.sql | 5 --
src/test/regress/sql/collate.linux.utf8.sql | 5 --
22 files changed, 8 insertions(+), 344 deletions(-)