fix: remove duplicate secret definition, update kustomization.yaml (#58)

cluster/core/cert-manager/kustomization.yaml

@@ -4,4 +4,4 @@ resources:
   - helm-release.yaml
   - letsencrypt-production.yaml
   - letsencrypt-staging.yaml
-  - secret.enc.yaml
+  - secret.sops.yaml

cluster/core/cert-manager/secret.enc.yaml

@@ -1,8 +0,0 @@
-# yamllint disable
-apiVersion: v1
-kind: Secret
-metadata:
-  name: cloudflare-token-secret
-  namespace: cert-manager
-stringData:
-  cloudflare-token: ${BOOTSTRAP_CLOUDFLARE_TOKEN}