make monitoring_config enable_components optional

.changelog/8299.txt

@@ -0,0 +1,4 @@
+```release-note:bug
+container: made `monitoring_config.enable_components` optional on `google_container_cluster` (GA)
+
+```

google/resource_container_cluster_test.go

@@ -2405,6 +2405,15 @@ func TestAccContainerCluster_withMonitoringConfig(t *testing.T) {
 				ImportStateVerify:       true,
 				ImportStateVerifyIgnore: []string{"min_master_version"},
 			},
+			{
+				Config: testAccContainerCluster_withMonitoringConfigPrometheusOnly2(clusterName),
+			},
+			{
+				ResourceName:            "google_container_cluster.primary",
+				ImportState:             true,
+				ImportStateVerify:       true,
+				ImportStateVerifyIgnore: []string{"min_master_version"},
+			},
 			{
 				Config: testAccContainerCluster_basic(clusterName),
 			},
@@ -6421,6 +6430,21 @@ resource "google_container_cluster" "primary" {
 `, name)
 }
 
+func testAccContainerCluster_withMonitoringConfigPrometheusOnly2(name string) string {
+	return fmt.Sprintf(`
+resource "google_container_cluster" "primary" {
+  name               = "%s"
+  location           = "us-central1-a"
+  initial_node_count = 1
+  monitoring_config {
+         managed_prometheus {
+                enabled = true
+         }
+  }
+}
+`, name)
+}
+
 func testAccContainerCluster_withSoleTenantGroup(name string) string {
 	return fmt.Sprintf(`
 resource "google_compute_node_template" "soletenant-tmpl" {

google/services/container/resource_container_cluster.go

@@ -962,7 +962,8 @@ func ResourceContainerCluster() *schema.Resource {
 					Schema: map[string]*schema.Schema{
 						"enable_components": {
 							Type:        schema.TypeList,
-							Required:    true,
+							Optional:    true,
+							Computed:    true,
 							Description: `GKE components exposing metrics. Valid values include SYSTEM_COMPONENTS, APISERVER, CONTROLLER_MANAGER, and SCHEDULER.`,
 							Elem: &schema.Schema{
 								Type:         schema.TypeString,