Make MIG's distribution_policy_zones configurable

[HauserV]

TL;DR

Remove the lifecycle policy to ignore changes in distribution_policy_zones from the MIG module.

Terraform Resources

• google_compute_region_instance_group_manager

Detailed design

N/A

Additional information

The policy was implemented to prevent re-creation of the resource on every apply in #28 but this has been fixed upstream GoogleCloudPlatform/magic-modules#12050.