cert manager changes based on review comments

app/models/clusters/applications/cert_manager.rb

@@ -39,10 +39,14 @@ module Clusters
 
       def cluster_issuer_file
         {
-          'cluster_issuer.yaml': cluster_issuer_content.deep_merge(cluster_issue_overlay)
+          'cluster_issuer.yaml': cluster_issuer_yaml_content
         }
       end
 
+      def cluster_issuer_yaml_content
+        YAML.dump(cluster_issuer_content.deep_merge(cluster_issue_overlay))
+      end
+
       def cluster_issuer_content
         YAML.load_file(cluster_issuer_file_path)
       end