Bump github.com/grafana/loki from 1.6.2-0.20230216091802-4e4359e67c6c to 6.7.8+incompatible in /tools/lambda-promtail

Bump github.com/grafana/loki from 1.6.2-0.20230216091802-4e4359e67c6c to 6.7.8+incompatible in /tools/lambda-promtail #8