pgsql: Fix ancient typo in user-defined-aggregates documentation.

Fix ancient typo in user-defined-aggregates documentation.

The description of the initcond value for the built-in avg(float8)
aggregate has been wrong since it was written.  Noted by Disc Magnet.

Branch
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REL9_0_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/6d0877fc5e5847e272129eb23ae48246ca352d2a

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