pgsql: Fix ordering/categorization of some recently-added system views.

Fix ordering/categorization of some recently-added system views.

Somebody added pg_replication_origin, pg_replication_origin_status and
pg_replication_slots to catalogs.sgml without a whole lot of concern for
either alphabetical order or the difference between a table and a view.
Clean up the mess.

Back-patch to 9.5, not so much because this is critical as because if
I don't it will result in a cross-branch divergence in release-9.5.sgml,
which would be a maintenance hazard.

Branch
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REL9_5_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/e4a58520fc3328455b46cf9bf589904133faa016

Modified Files
--------------
doc/src/sgml/catalogs.sgml            | 494 +++++++++++++++++-----------------
doc/src/sgml/high-availability.sgml   |   2 +-
doc/src/sgml/logicaldecoding.sgml     |   2 +-
doc/src/sgml/release-9.5.sgml         |   2 +-
doc/src/sgml/replication-origins.sgml |   2 +-
5 files changed, 251 insertions(+), 251 deletions(-)