Include the 64TiB PD disk size as a supported PD type

[pablogarciaarevalo]

The Terraform doc states the below:
disk_size_size - (Optional) The required size of the disks. For GB, the unit can be: [100 or 500]. For TB, the unit can be: [1,2,4,8,16]. The default is '1'

It should include the 64 TiB disks as a supported persistent disks in Google Cloud according to the documentation.

[chuyich]

Raised DEVOPS-7288 for tracking this issue.