[OCPBUGS-45747]: Fixing command in HCP docs

Author: lahinson

modules/hcp-bm-add-np.adoc

@@ -19,13 +19,13 @@ $ hcp create nodepool agent \
   --cluster-name <hosted_cluster_name> \// <1>
   --name <nodepool_name> \// <2>
   --node-count <worker_node_count> \// <3>
-  --agentLabelSelector '{"matchLabels": {"size": "medium"}}' <4>
+  --agentLabelSelector size=medium <4>
 ----
 +
 <1> Replace `<hosted_cluster_name>` with your hosted cluster name.
 <2> Replace `<nodepool_name>` with the name of your node pool, for example, `<hosted_cluster_name>-extra-cpu`.
 <3> Replace `<worker_node_count>` with the worker node count, for example, `2`.
-<4> The `--agentLabelSelector` flag is optional. The node pool uses agents with the `"size" : "medium"` label.
+<4> The `--agentLabelSelector` flag is optional. The node pool uses agents with the `size=medium` label.
 
 . Check the status of the node pool by listing `nodepool` resources in the `clusters` namespace:
 +