Update category_featured_topic.rb (PR #10121)

Only made one change, catching ActiveRecord::RecordNotUnique as well as the pre-existing PG::UniqueViolation

In my experience, does not catch the PG::UniqueViolation as ActiveRecord::RecordNotUnique is on top of it, so you should have both. I ran into this problem when creating large amounts of topics at the same time (I usually find this downstream in the source code when I pull it and change it there after each git clone)

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Thanks, this seems good.