Replace `github.action_path` with `GITHUB_ACTION_PATH`

[suzuki-shunsuke]

• https://github.com/search?q=owner%3Asuzuki-shunsuke%20github.action_path&type=code
• https://github.com/actions/runner/issues/716#issuecomment-795238933
• https://github.com/suzuki-shunsuke/tfaction/pull/1740#issuecomment-2229518246

[suzuki-shunsuke]

• https://github.com/suzuki-shunsuke/github-action-terraform-init/pull/18
• https://github.com/suzuki-shunsuke/github-action-format/pull/690
• https://github.com/suzuki-shunsuke/github-action-terraform-fmt/pull/17