Notifications are sent to sponsor when they should be sent to proxy

Overview:

When a proxy-sponsor relationship is created, notifications can be set to send either to the sponsor or the proxy. However, when they are set to be sent to the proxy, they are still sent to the sponsor.
Steps to Reproduce:

1. Log into some FOLIO environment
2. Create a proxy/sponsor relationship between 2 users.
3. Set notifications to be sent to the proxy.
4. Perform an action (e.g. checkout an item or make a request) that will cause a notification to be sent.

Expected Results:

Notifications are sent to proxy.
Actual Results:

Notifications are sent to sponsor.
Additional Information:

Reproducible in Lotus Bugfest.
URL: https://bugfest-lotus.int.aws.folio.org

May be more of a circulation issue, but created initially for mod-users since that's the module that contains proxy-sponsor relationships.