fixup! Migrate cluster modules from map(map(string)) to map(object)

Author: pst

google/_modules/gke/variables.tf

@@ -301,4 +301,5 @@ variable "guest_accelerator" {
     }))
   })
   description = "`guest_accelerator` block supports during node_group creation, useful to provision GPU-capable nodes. Default to `null` or `{}` which will disable GPUs."
+  default     = null
 }