Revert:Use N4 (gen4) machines as default to create GKE system nodepool (#5425)

Author: aslam-quad

modules/scheduler/gke-cluster/README.md

@@ -202,7 +202,7 @@ limitations under the License.
 | <a name="input_system_node_pool_enabled"></a> [system\_node\_pool\_enabled](#input\_system\_node\_pool\_enabled) | Create a system node pool. | `bool` | `true` | no |
 | <a name="input_system_node_pool_image_type"></a> [system\_node\_pool\_image\_type](#input\_system\_node\_pool\_image\_type) | The default image type used by NAP once a new node pool is being created. Use either COS\_CONTAINERD or UBUNTU\_CONTAINERD. | `string` | `"COS_CONTAINERD"` | no |
 | <a name="input_system_node_pool_kubernetes_labels"></a> [system\_node\_pool\_kubernetes\_labels](#input\_system\_node\_pool\_kubernetes\_labels) | Kubernetes labels to be applied to each node in the node group. Key-value pairs.<br/>(The `kubernetes.io/` and `k8s.io/` prefixes are reserved by Kubernetes Core components and cannot be specified) | `map(string)` | `null` | no |
-| <a name="input_system_node_pool_machine_type"></a> [system\_node\_pool\_machine\_type](#input\_system\_node\_pool\_machine\_type) | Machine type for the system node pool. | `string` | `"n4-standard-4"` | no |
+| <a name="input_system_node_pool_machine_type"></a> [system\_node\_pool\_machine\_type](#input\_system\_node\_pool\_machine\_type) | Machine type for the system node pool. | `string` | `"e2-standard-4"` | no |
 | <a name="input_system_node_pool_name"></a> [system\_node\_pool\_name](#input\_system\_node\_pool\_name) | Name of the system node pool. | `string` | `"system"` | no |
 | <a name="input_system_node_pool_node_count"></a> [system\_node\_pool\_node\_count](#input\_system\_node\_pool\_node\_count) | The total min and max nodes to be maintained in the system node pool. | <pre>object({<br/>    total_min_nodes = number<br/>    total_max_nodes = number<br/>  })</pre> | <pre>{<br/>  "total_max_nodes": 10,<br/>  "total_min_nodes": 2<br/>}</pre> | no |
 | <a name="input_system_node_pool_taints"></a> [system\_node\_pool\_taints](#input\_system\_node\_pool\_taints) | Taints to be applied to the system node pool. | <pre>list(object({<br/>    key    = string<br/>    value  = any<br/>    effect = string<br/>  }))</pre> | <pre>[<br/>  {<br/>    "effect": "NO_SCHEDULE",<br/>    "key": "components.gke.io/gke-managed-components",<br/>    "value": true<br/>  }<br/>]</pre> | no |

modules/scheduler/gke-cluster/variables.tf

@@ -261,7 +261,7 @@ variable "system_node_pool_node_count" {
 variable "system_node_pool_machine_type" {
   description = "Machine type for the system node pool."
   type        = string
-  default     = "n4-standard-4"
+  default     = "e2-standard-4"
 }
 
 variable "system_node_pool_disk_size_gb" {