Fix bogus logic for skipping unnecessary partcollation dependencies.

Fix bogus logic for skipping unnecessary partcollation dependencies.

The idea here is to not call recordDependencyOn for the default collation,
since we know that's pinned.  But what the code actually did was to record
the partition key's dependency on the opclass twice, instead.

Evidently introduced by sloppy coding in commit 2186b608b.  Back-patch
to v10 where that came in.