Update terraform GCP to Ubuntu 20.04 (latest LTS) (#8463)

* Fix terraform Warning

Version constraints inside provider configuration blocks are deprecated

Terraform 0.13 and earlier allowed provider version constraints inside the
provider configuration block, but that is now deprecated and will be removed
in a future version of Terraform. To silence this warning, move the provider
version constraint into the required_providers block.

* Fix terraform Warning: Quoted references are deprecated

* terraform: Update GCP Ubuntu to latest LTS