Slack Integration: error event links to latest error instead of actual timestamped error instance

### Environment

SaaS (https://sentry.io/)

### Version

_No response_

### Steps to Reproduce

`"@sentry/node": "5.30.0"`

1. have a sentry error grouped by message. These errors are built with `Sentry.captureEvent` from `@sentry/node`. They have the same message but we add different values under `extras: {splat}`
2. have these errors reported in a slack channel through slack integration
3. have the error triggering more than once (triggering for different reasons - meaning the values under splat are different, but the error message is the same)

### Expected Result

if the error posted in slack is part of the same group (grouped by message) **the link of each instance of that error in the slack message is unique and leads to that instance and timestamp of that error** instead of the most recent event of that group

### Actual Result

if the error posted in slack is part of the same group (grouped by message) the link of both instances of that error in the slack message **is the same and leads to the most recent timestamp event of that group**. So two different events of that error that happened in 2 different timestamps have the same link which is connected to the latest instance of that error.

┆Issue is synchronized with this [Jira Improvement](https://getsentry.atlassian.net/browse/FEEDBACK-2084) by [Unito](https://www.unito.io)