fix: disable cert-manager webhook for pvc-autoresizer, use self-signed cert [ci skip]

Cluster doesn't have cert-manager installed. Use self-signed certificate
for the controller and disable the PVC mutating webhook (annotations are
set directly on PVCs via Terraform).

stacks/pvc-autoresizer/modules/pvc-autoresizer/main.tf

@@ -35,5 +35,13 @@ resource "helm_release" "pvc_autoresizer" {
         }
       }
     }
+    webhook = {
+      certificate = {
+        generate = true
+      }
+      pvcMutatingWebhook = {
+        enabled = false
+      }
+    }
   })]
 }