Bump production composer image to composer-2.8.6-airflow-2.6.3 (#4068)

Author: ohrite

iac/cal-itp-data-infra/composer/us/environment.tf

@@ -36,7 +36,7 @@ resource "google_composer_environment" "calitp-composer" {
     environment_size = "ENVIRONMENT_SIZE_SMALL"
 
     software_config {
-      image_version = "composer-2.8.3-airflow-2.6.3"
+      image_version = "composer-2.8.6-airflow-2.6.3"
 
       airflow_config_overrides = {
         celery-worker_concurrency                  = 4