[Gitar] Cleaning up stale feature flag: slack-integration with value true

[gitar-bot-staging[bot]]

Feature Flag Cleanup

| Stale Flag | Value | | ---------- | ------- | | slack-integration | true |

Trigger

https://github.com/gitarcode/growthbook/issues/59#issuecomment-2092000619

Bot Commands

`@gitar-bot cleanup stale_flag=value` will cleanup a stale feature flag. Replace `stale_flag` with the name of the stale feature flag and `value` with either `true` or `false`.