fix: update gce-vpc to use random suffix

[glasnt]

No description provided.

[glasnt]

Re: change in 9af2904:

  on .terraform/modules/dynamic-python-webapp.gce-vpc/modules/subnets/main.tf line 29, in resource "google_compute_subnetwork" "subnetwork":
  29:   for_each                   = local.subnets
    ├────────────────
    │ local.subnets will be known only after apply

The "for_each" map includes keys derived from resource attributes that cannot
be determined until apply, and so Terraform cannot determine the full set of
keys that will identify the instances of this resource.

This is coming from the module itself. I added dynamic variables to the network, subnet, and instance because I thought that would be appropriate, but if subnets only need to be unique within the network, then making the subnet static should still allow for multiple deployments (in this scope).