Old and insecure Grafana and Prometeus versions

```
$ grep -E 'image: (prom|grafana)' docker-compose.yml 
    image: prom/pushgateway:v0.3.1
    image: prom/prometheus:v2.2.1
    image: grafana/grafana:6.0.1
```

See also:
- https://github.com/grafana/grafana/security/advisories
- https://grafana.com/blog/2021/12/10/grafana-8.3.2-and-7.5.12-released-with-moderate-severity-security-fix/