A trivial fix on a comment in pgstat_assoc_relation()

Hi,

I noticed that a comment in pgstat_assoc_relation() starts with "Else":

/* Else find or make the PgStat_TableStatus entry, and update link */

This seems to be a vestige from when this function was split out from pgstat_init_relation()
by commit 5891c7a8ed8f, so I think we could simply remove the "Else".

Regards,
Yugo Nagata

-- 
Yugo Nagata <nagata@sraoss.co.jp>