feat(deps): Raise upper Terraform Google Provider bound to v8

[nika-pr]

Since nobody is looking to fix PR #535, this is my attempt to get the dependencies finally updated.

[rjw57]

Firstly, thanks @nika-pr for moving this forward as I'm sure there are many of us poor souls blocked from moving to provider v7 because of this. (For us, University of Cambridge DevOps, this is blocking updates for around 40 different terraform-driven deployments.)

I wonder if this PR may even be bolder by removing the < 8 restriction from the provider version and only define a minimum version? X-posting my observation from #538: terraform's best practice guide for version requirements recommends that reusable modules only specify a minimum version requirement:

Reusable modules should constrain only their minimum allowed versions of Terraform and providers, such as >= 0.12.0. This helps avoid known incompatibilities, while allowing the user of the module flexibility to upgrade to newer versions of Terraform without altering the module.

(my emphasis)

[apeabody]

/gcbrun

[imrannayer]

fixed in #556