Alert should have been triggered by an issue, but it did not

### Environment

SaaS (https://sentry.io/)

### Steps to Reproduce

1. Set up an alert that should trigger when the number of events in an issue is more than 3 in 15m
2. An issue met this condition, but when the events came in so close together the query didn't catch them all and the alert didn't trigger

Please find an example and additional information in the Jira shadow ticket.

### Expected Result

The alert should trigger in every case when the condition is met

### Actual Result

The alert did not trigger

### Product Area

Alerts

### Link

_No response_

### DSN

_No response_

### Version

_No response_

┆Issue is synchronized with this [Jira Improvement](https://getsentry.atlassian.net/browse/FEEDBACK-2380) by [Unito](https://www.unito.io)

Start with the reproduction steps and the Jira shadow ticket FEEDBACK-2380, focusing on the Alerts product area and the missed query results when events arrive close together. Done means identifying and correcting the alert behavior so every issue meeting the more-than-3-events-in-15m condition triggers an alert, with verification of the reported case.

Written by the indexing model from the issue text.