pgsql: Update doc mention of how to compute bigint advisory lock value,

Update doc mention of how to compute bigint advisory lock value, per Tom
Lane's correction.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/5ea6c9d79882815d4cc1c3c302f415eb637466f2

Modified Files
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doc/src/sgml/catalogs.sgml | 4 ++--
1 files changed, 2 insertions(+), 2 deletions(-)