Minor typo fix (#939)

Promnetheus -> Prometheus

docs/Monitoring external etcd.md

@@ -13,7 +13,7 @@ Prometheus Operator allows us to mount secrets in the pod. By loading the secret
 where CREDENTIAL_PATH is the path to your etcd client credentials on your work machine. 
 (Kube-aws stores them inside the credential folder).
 
-## b - Get Promnetheus Operator to load the secret
+## b - Get Prometheus Operator to load the secret
 In the previous step we have named the secret 'etcd-certs'.
 
 Edit prometheus-operator/contrib/kube-prometheus/manifests/prometheus/prometheus-k8s.yaml and add the secret under the spec of the Prometheus object manifest:
@@ -167,4 +167,4 @@ Once you are happy with the dashboard, export it and move it to `prometheus-oper
 ### Reload the manifest in Kubernetes:
 ` kubectl -n monitoring replace -f manifests/grafana/grafana-dashboards.yaml`
 
-After a few minutes your dasboard will be available permanently to all Grafana instances
\ No newline at end of file
+After a few minutes your dasboard will be available permanently to all Grafana instances