[Bug report]: Generate the correct amount of event deliveries

[subomi]

Describe the bug

I'm experiencing an issue where we are generating more event deliveries than required for a particular event.

To Reproduce

Steps to reproduce the behaviour:

1. Create an Outgoing Project and set Allow endpoint have multiple subscriptions to true.
2. Register one endpoint and two subscriptions.
3. Turn Allow endpoint have multiple subscriptions off.
4. Delete one of the associated subscriptions.
5. Send an event; instead of getting one event delivery, we get two.

Expected behavior

I expected to get one event delivery after deleting the other subscription, but I got two event deliveries.