Bulk Transactions Items iterator returns keys instead of Items

[philvarner]

stac-fastapi/stac_fastapi/extensions/stac_fastapi/extensions/third_party/bulk_transactions.py

Line 21 in 33611f7

return iter(self.items)

in Bulk Transactions, the Items iterator returns an iterator over the keys in the items dictionary. This isn't very useful and (I would say) unexpected, as I'd expect to get an iterator of the Items objects instead (the values of that dict).