pgsql: doc: Remove event trigger firing matrix

doc: Remove event trigger firing matrix

This is difficult to maintain accurately, and it was probably already
somewhat incorrect, especially in the sql_drop and table_rewrite
categories.

The prior section already documented which DDL commands are *not*
supported (which was also slightly outdated), so let's expand that a
bit and just rely on that instead of listing out each command in full
detail.

Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Michael Paquier <michael@paquier.xyz>
Reviewed-by: Jian He <jian.universality@gmail.com>
Discussion:
https://www.postgresql.org/message-id/flat/CACJufxE_UAuxcM08BW5oVsg34v0cFWoEt8yBa5xSAoKLmL6LTQ%40mail.gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/a0be94067e76c81a2bbba6a98b584b870024e363

Modified Files
--------------
doc/src/sgml/event-trigger.sgml      | 1028 +++-------------------------------
src/backend/commands/event_trigger.c |    4 +-
src/backend/tcop/utility.c           |    3 +
3 files changed, 81 insertions(+), 954 deletions(-)