A file in `ISSUE_TEMPLATE` with the name `config.yml` shouldn't be treated as a YAML template, it's for [configuring the template chooser](https://docs.github.com/en/communities/using-templates-to-encourage-useful-issues-and-pull-requests/configuring-issue-templates-for-your-repository#configuring-the-template-chooser). The old code tried to ignore the file, but it didn't work, caused by #20987. That's why the warning is displayed: <img width="415" alt="image" src="https://user-images.githubusercontent.com/9418365/202094067-804c42fe-0e9e-4fc5-bf01-d95fa336f54f.png"> Note that this PR is not an implementation of `config.yml`, there will be another one to do it.
