pgsql: Fix docs on lock level for ALTER TABLE VALIDATE

pgsql: Fix docs on lock level for ALTER TABLE VALIDATE

Fix docs on lock level for ALTER TABLE VALIDATE

ALTER TABLE .. VALIDATE CONSTRAINT previously
gave incorrect details about lock levels and
therefore incomplete reasons to use the option.

Initial bug report and fix from Marko Tiikkaja
Reworded by me to include comments by Kevin Grittner

Branch
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REL9_1_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/be039d4b29be88a7f8b57d6353c81bced54d1b83

Modified Files
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doc/src/sgml/ref/alter_table.sgml |   10 +++++++---
1 file changed, 7 insertions(+), 3 deletions(-)