pgsql: Backpatch doc change SYMETRIC -> SYMMETRIC, for 8.2.X.

Log Message:
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Backpatch doc change SYMETRIC -> SYMMETRIC, for 8.2.X.

Tags:
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REL8_2_STABLE

Modified Files:
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pgsql/doc/src/sgml:
func.sgml (r1.347.2.6 -> r1.347.2.7)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/doc/src/sgml/func.sgml.diff?r1=1.347.2.6&r2=1.347.2.7)