documentation/prometheus-mixin: fix comment typo
// If you run Prometheus on Kubernetes with the Prometheus
// Operator, you can make use of the configured target labels for
// nicer naming:
- // prometheusNameTemplate: '{{$labels.namespace}}/{{$labels.pod}}'
+ // prometheusName: '{{$labels.namespace}}/{{$labels.pod}}'
// prometheusHAGroupName is inserted into annotations to name an
// HA group. All labels used here must also be present in
