Update to Terraform 1.0.7 and terraform-docs v0.15.0

[dav3r]

🗣 Description

This PR updates our global Terraform version from 0.14.11 to 1.0.7. It also updates our global terraform-docs version from v0.14.1 to v0.15.0.

💭 Motivation and context

This is the last step in our journey of migrating Terraform to version 1.0.x. We previously upgraded from Terraform 0.12 to 0.13 with #37 and from 0.13 to 0.14 in #39.

This PR will remain blocked until the following conditions have been met:

• All of our repositories that use Terraform have been successfully updated to use Terraform 1.0.x.
• All of our deployed Terraform states have been updated to Terraform 1.0.x.

This PR is part of https://github.com/cisagov/cool-system/issues/219.

🧪 Testing

These is not really anything to test in this repository, but this change will be verified in all downstream repositories that use these TERRAFORM_VERSION and TERRAFORM_DOCS_VERSION values.

✅ Checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All new and existing tests pass.
• All downstream repositories have successfully applied with Terraform 1.0.x in every workspace of every Terraform directory.

✅ Post-Merge Checklist

• Make PRs in cisagov/skeleton-tf-module, cisagov/skeleton-packer, and cisagov/skeleton-ansible-role-with-test-user to revert all references from cisagov/setup-env-github-action@improvement/support_tf_1.0 to cisagov/setup-env-github-action@develop.
• Delete old branches improvement/support_tf_0.13 and improvement/support_tf_0.14.

[jsf9k]

Powerful work!

[mcdonnnj]