Modified acme-cluster-issuer yaml file to add ingress class name

modules/cert-manager-acme-http01.adoc

@@ -35,13 +35,23 @@ spec:
     solvers:
     - http01:
         ingress:
-          class: openshift-default                                 <4>
+          ingressClassName: openshift-default                                 <4>
 ----
 <1> Provide a name for the cluster issuer.
 <2> Replace `<secret_private_key>` with the name of secret to store the ACME account private key in.
 <3> Specify the URL to access the ACME server's `directory` endpoint. This example uses the _Let's Encrypt_ staging environment.
 <4> Specify the Ingress class.
 
+[NOTE]
+====
+If created without specifying `ingressClassName`, use the following command to patch the existing ingress:
+
+[source,terminal]
+----
+$ oc patch ingress/<ingress-name> --type=merge --patch '{"spec":{"ingressClassName":"openshift-default"}}' -n <namespace>
+----
+====
+
 .. Create the `ClusterIssuer` object by running the following command:
 +
 [source,terminal]