Fix bug in generate_docs function
Fix bug in generate_docs function

The generate_docs function would attempt to run terraform_docs against
the autogen/ directory. Since that directory contains templates instead
of actual working Terraform, the terraform-docs command failed, causing
no docs to be properly formatted.

These changes update the function to properly ignore the ./autogen
directory.

terraform-google-modules/terraform-google-kubernetes-engine,terraform-google-modules/terraform-google-kubernetes-engine,terraform-google-modules/terraform-google-kubernetes-engine