Since pg_depend can contain duplicate entries, we need to eliminate
those in information schema views that build on pg_depend, using
DISTINCT.  Some of the older views already did that correctly, but
some of the more recently added ones didn't.  (In some of these views,
it might not be possible to reproduce the issue because of how the
implementation happens to deduplicate dependencies while recording
them, but it seems better to keep this consistent in all cases.)