move cluster maintenance window

To avoid GMT/BST issues, move the maintenance window from 4-8AM UTC to
2-5AM UTC.

Closes #11

main.tf

@@ -79,8 +79,8 @@ resource "google_container_cluster" "cluster" {
   maintenance_policy {
     recurring_window {
       recurrence = "FREQ=WEEKLY;BYDAY=MO,TU,WE,TH,FR,SA,SU"
-      end_time   = "2020-01-28T08:00:00Z"
-      start_time = "2020-01-28T04:00:00Z"
+      end_time   = "2020-01-28T05:00:00Z"
+      start_time = "2020-01-28T02:00:00Z"
     }
   }
 }