Summary:
Helps with cases such as https://grist.slack.com/archives/C02EGJ1FUCV/p1652196111066649?thread_ts=1651656433.171889&cid=C02EGJ1FUCV
When a user unsubscribes from a webhook, the secret URL is deleted from the database, but as long as the doc was open it would continue retrying pending requests still in the queue for a long time, using the locally cached value without noticing the effect of unsubscribing. This change allows unsubscribing to have an effect more quickly so that problematic events can be removed from the queue.
Test Plan: existing tests
Reviewers: paulfitz
Reviewed By: paulfitz
Differential Revision: https://phab.getgrist.com/D3430