deleting the space and updating citations and bibliography, should properly group the citations.
Added in edit.
This may confuse the collaborator when you return the document, but if you export the traveling library, and update the citations in the document, with that traveling library open, it links to that version. - you can unformat and reformat with that exported library. – Also you can change your preferences, to use page numbers and this might be invisible to him. It is all in the order you do these steps.