pgsql: Remove comment about modifying tab-complete.c for userset GUC.

Log Message:
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Remove comment about modifying tab-complete.c for userset GUC.

Simon Riggs

Modified Files:
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pgsql/src/backend/utils/misc:
guc.c (r1.397 -> r1.398)
(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/backend/utils/misc/guc.c.diff?r1=1.397&r2=1.398)