Restrict Terraform / OpenTofu format check to known Terraform files
This fixes the following issue:
│ Only .tf, .tofu, .tfvars, .tftest.hcl, and .tofutest.hcl files can be │ processed with tofu fmt
Test Plan: pre-commit run tf-format --all-files -v in rOPS
Differential Revision: https://devcentral.nasqueron.org/D4164