pgsql: Add C comment that we will have to remove an exclusion constraint

Log Message:
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Add C comment that we will have to remove an exclusion constraint check
if we ever implement '<>' index opclasses.

Jeff Davis

Modified Files:
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pgsql/src/backend/executor:
execUtils.c (r1.171 -> r1.172)
(http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/src/backend/executor/execUtils.c?r1=1.171&amp;r2=1.172)