pgsql: doc: Add ALTER/DROP ROUTINE to the event trigger matrix

doc: Add ALTER/DROP ROUTINE to the event trigger matrix

ALTER ROUTINE triggers the events ddl_command_start and ddl_command_end,
and DROP ROUTINE triggers sql_drop, ddl_command_start and
ddl_command_end, but this was not mention on the matrix table.

Reported-by: Leslie Lemaire
Discussion: /messages/by-id/164647533363.646.5802968483136493025@wrigleys.postgresql.org
Backpatch-through: 11

Branch
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REL_12_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/2cd7d8d53079cd74f0151465be316a94993d1218

Modified Files
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doc/src/sgml/event-trigger.sgml | 16 ++++++++++++++++
1 file changed, 16 insertions(+)