* internal/getproviders: Add URL to error message for clarity
Occasionally `terraform init` on some providers may return the following error message:
Error while installing citrix/citrixadc v1.13.0: could not query provider
registry for registry.terraform.io/citrix/citrixadc: failed to retrieve
authentication checksums for provider: 403 Forbidden
The 403 is most often returned from GitHub (rather than Registry API)
and this change makes it more obvious.
* Use Host instead of full URL