Fix documentation of environment variable defaults (#6536)
Fix documentation of environment variable defaults (#6536)

For some reason, the `-` character was missing here in the documentation.
After struggling for some time, I finally figured out that -- quite obviously -- envsubst default behavior applies and thus the documentation was wrong. :-)
grafana/loki,grafana/loki,grafana/loki,grafana/loki,grafana/loki,grafana/loki