Remove the redundant yaml file

config/cert_manager/cluster_issuer.yaml

-apiVersion: certmanager.k8s.io/v1alpha1
-kind: ClusterIssuer
-metadata:
-  name: letsencrypt-prod
-spec:
-  acme:
-    server: https://acme-v02.api.letsencrypt.org/directory
-    email: my-email@example.com
-    privateKeySecretRef:
-      name: letsencrypt-prod
-    http01: {}