errata shouldn't overwrite references

[michamos]

currently, errata overwrite references from the main published paper due to https://github.com/inspirehep/inspire-json-merger/blob/402974ba11a6ac976ca2bf5b5809ee107731d2f9/inspire_json_merger/config.py#L327. That filter should be removed, so all references are kept, with the errata references appearing at the end of the list (should be the default behavior based on https://github.com/inspirehep/inspire-json-merger/blob/402974ba11a6ac976ca2bf5b5809ee107731d2f9/inspire_json_merger/config.py#L331)