Update relations.py
Update relations.py

@dustine32 @kltm @pgaudet

I'm proposing more edits to the relations.py file in anticipation of corrections curators will make to their annotation extensions that currently use the 'exists during' relation.
I've added a line for the RO relation 'existence starts and ends during' and updated the 'exists during' ID to point to the gorel id.
Please let me know if you foresee any issues; I just wanted to add this so we don't start flagging valid AE relations as invalid like we did a few weeks ago for the PomBase annotations.

Thanks.
biolink/ontobio,biolink/ontobio