TODO: Revert back `terraform-docs` repo

[michaelsaki]

💡 Summary

We need to revert back to using the main terraform-docs repo after terraform-docs/terraform-docs#745 has been merged.

Motivation and context

We are currently using a forked branch @mcdonnnj made to allow ATX header support for terraform-docs. Once his branch has been approved we should revert back to the standard of pulling from the main repo of terraform-docs.

Implementation notes

Implementation would be as follows:

• edit the build.yml workflow to pull from the main repo of terraform-docs
• this is a TODO from Add ATX Header Support for terraform-docs #164

Acceptance criteria

• Add support for closed ATX headers in Markdown output terraform-docs/terraform-docs#745 has been merged into the main repo of terraform-docs
• the workflow has been reverted back to use the main repo of terraform-docs
• clean up any unnecessary variables or comments that were made during Add ATX Header Support for terraform-docs #164