fix: Allow disabling instance refresh on self-managed node groups (part deux) (#3478)

variables.tf

@@ -841,14 +841,7 @@ variable "self_managed_node_groups" {
       }))
       strategy = optional(string)
       triggers = optional(list(string))
-      }),
-      # Default
-      {
-        strategy = "Rolling"
-        preferences = {
-          min_healthy_percentage = 66
-        }
-      }
+      })
     )
     use_mixed_instances_policy = optional(bool)
     mixed_instances_policy = optional(object({