Fix/ ARR Ethics_Reviewers Invite_Assignment

[celestemartinez]

Changes:

• add is_ethics_reviewer variable to invite assignment invitation so emails are sent with proper committee name
• add ethics chairs as signatures of the Ethics_Chairs group so they can sign Invite_Assignment edges
• remove edge_readers and edge_writers and pass None for these two fields (use openreview.api.Edge instead of openreview.Edge)

[celestemartinez]

@haroldrubio you should be able to run this to create the emergency ethics reviewers groups instead of manually posting them:

venue.group_builder.set_external_reviewer_recruitment_groups(name=f'Emergency_{venue.get_ethics_reviewers_name(pretty=False)}')