Fix regex pipeline-example.yml (#1707)
Fix regex pipeline-example.yml (#1707)

Backslashes must not be escaped inside single quotes:
https://github.com/grafana/loki/blob/master/docs/clients/promtail/stages/regex.md#schema

Spent an hour trying to figure out why no `level` tags assigned to my logs. Worked fine after the fix.
grafana/loki,grafana/loki,grafana/loki,grafana/loki,grafana/loki,grafana/loki