Update the high availability docs to use the correct label

Author: bkimbrough88

doc/content/en/04-administration-guide/09-high-availability/_index.md

@@ -36,7 +36,7 @@ There are two different ways to accomplish this. The first one is with the `kube
 To identify the primary node:
 
 ```
-$ kubectl get pods -n default -l app=StackGresCluster -l role=master
+$ kubectl get pods -n default -l app=StackGresCluster -l role=primary
 NAME          READY   STATUS    RESTARTS   AGE
 stackgres-0   5/5     Running   0          165m
 ```
@@ -76,4 +76,4 @@ We can retrieve some valuable information here:
 - Who are the replica nodes
 - The IP address and port
 - The state of each node
-- The lag in MB in case some nodes are not up-to-date
+- The lag in MB in case some nodes are not up-to-date