collab: Ignore Stripe events that are older than an hour (#15830)

This PR makes it so any Stripe events we receive that occurred over an
hour ago are marked as processed.

We don't want to process an old event long after it occurred and
potentially overwrite more recent updates.

This also makes running collab locally a bit nicer, as we won't be
getting errors for a bunch of older events that will never get processed
successfully.

The period after time after which we consider an event "stale" can be
modified, as needed.

Release Notes:

- N/A