Remove #alerts channel Alertmanager integrations
The #alerts channel in Slack is effectively `/dev/null` for notifications. We need to develop a plan for addressing alerts that are configured to spam this channel.
_How do we?_
- Determine which alerts can be safely removed?
- Determine which alerts should be directed elsewhere?
- Determine which alerts are captured with Service Metrics Catalogue?
## Definition of Done
- [ ] The #alerts channel is silent from Alertmanager
- [ ] The #alerts channel is archived
issue