Add South Central US to trusted FXCI provisioners

[jwmossmoz]

Summary

• Add South Central US to every trusted FXCI provisioner location map (comm-3, enterprise-3, gecko-3, mozilla-3, nss-3, and vpn-3).
• Remove stale commented-out region entries from those maps so terraform fmt produces clean alignment.
• Include the refreshed Terraform lockfiles for the touched trusted provisioner directories.

Context

This supports mozilla-releng/fxci-config#1002, which can schedule trusted workers in South Central US. Without the matching Terraform-managed resource groups, virtual networks, and subnets, Azure NIC creation can fail with missing subnet errors such as vn-south-central-us-gecko-3/subnets/sn-south-central-us-gecko-3 referenced ... was not found.

Validation

• terraform fmt on the touched trusted FXCI main.tf files
• git diff --check