Fix wrong zip compress format for Terraform registry

[KeisukeYamashita]

WHAT

As title.

How to reproduce

Make sure that you have Terraform version upper than 0.13.0.

$ terraform version
Terraform v0.13.1

And then write a provider block.

terraform {
  required_providers {
    miro = {
      source = "mercari/spinnaker"
    }
  }
}

provider "spinnaker" {
  gate_endpoint = "https://spinnaker.nokisai.com"
}

Run below.

$ terraform init
Initializing the backend...

Initializing provider plugins...
- Finding latest version of mercari/spinnaker...
- Finding latest version of hashicorp/spinnaker...
- Installing mercari/spinnaker v0.2.3...


Error: Failed to install provider

Error while installing mercari/spinnaker v0.2.3: zip: not a valid zip file


Error: Failed to install provider

Error while installing hashicorp/spinnaker: provider registry
registry.terraform.io does not have a provider named
registry.terraform.io/hashicorp/spinnaker

WHY

The pull tgz format from the Terraform Registry is not currect, and not runnable.