Relax network CIDR validation

[miguelhar]

Allows for smaller CIDR ranges avoiding

Plan: 62 to add, 0 to change, 0 to destroy.
╷
│ Error: Invalid value for variable
│
│   on .terraform/modules/infra/modules/infra/main.tf line 67, in module "network":
│   67:   network             = var.network
│     ├────────────────
│     │ var.network.cidrs is object with 2 attributes
│
│ Each of network.cidrs must be a valid CIDR block.
│
│ This was checked by the validation rule at .terraform/modules/infra/modules/infra/submodules/network/variables.tf:80,3-13.