cmd/k8s-operator/deploy: clarify helm install notes (#16449)

Based on feedback that it wasn't clear what the user is meant to do with
the output of the last command, clarify that it's an optional command to
explore what got created.

Updates #13427

Change-Id: Iff64ec6d02dc04bf4bbebf415d7ed1a44e7dd658

Signed-off-by: Tom Proctor <tomhjp@users.noreply.github.com>

cmd/k8s-operator/deploy/chart/templates/NOTES.txt

@@ -22,4 +22,6 @@ $ kubectl explain proxyclass
 $ kubectl explain recorder
 $ kubectl explain dnsconfig
 
-$ kubectl --namespace={{ .Release.Namespace }} get pods
+If you're interested to explore what resources were created:
+
+$ kubectl --namespace={{ .Release.Namespace }} get all -l app.kubernetes.io/managed-by=Helm