fix: Remove fetching:collection listener

[villelahdenvuo]

We already hook into the Collection fetching event so that causes the query to be modified twice in some cases.

[bsiddiqui]

@villelahdenvuo if we remove this than deleting a collection won't trigger the soft delete. What modification are you making in the collection fetching event?

[villelahdenvuo]

@bsiddiqui in my tests the Collection's fetching event is called, the fetching:collection is a duplicate event for convenience.

[villelahdenvuo]

I mean: In Bookshelf Model#fetching:collection is a convenience event that is called when a Collection is fetched, but since we already hook into the Collection fetching event, we get duplicate events, one for the Collection and one for the Model of that collection (fetching:collection).

My tests catch this because we mock database queries and match them to expected SQL/regex and I saw that the where deleted_at is null clause was being duplicated. And it seems that all the tests in this repo pass, too, except for some issue with migrations, which seems unrelated?

[bsiddiqui]

Great, thanks! I tested locally and tests passed so I'll merge and fix circle later.