pgsql: Remove erroneous claim about use of pg_locks.objid for advisory

Remove erroneous claim about use of pg_locks.objid for advisory locks.

The correct information appears in the text, so just remove the statement
in the table, where it did not fit nicely anyway.  (Curiously, the correct
info has been there much longer than the erroneous table entry.)
Resolves problem noted by Daniele Varrazzo.

In HEAD and 9.1, also do a bit of wordsmithing on other text on the page.

Branch
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REL9_1_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/8ab9df0db196b6e1afa75838394eb27e9955e80e

Modified Files
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doc/src/sgml/catalogs.sgml |   48 ++++++++++++++++++++++---------------------
1 files changed, 25 insertions(+), 23 deletions(-)