pgsql: Correct mistaken claims about EXPLAIN ANALYZE's handling of trig

Correct mistaken claims about EXPLAIN ANALYZE's handling of triggers.

Time spent executing AFTER triggers is not included in the runtime of the
associated ModifyTable node; in my patch of yesterday I confused queuing of
these triggers with their actual execution.  Spotted by Marko Tiikkaja.

Branch
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REL9_0_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/a48fb0b59811e8b41e727b54b39bef28d6f253ea

Modified Files
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doc/src/sgml/perform.sgml |   11 +++++++----
1 files changed, 7 insertions(+), 4 deletions(-)