Remove CNAME from root dir to be more simpler because of ...

now switching to deploy from gh-pages branch.

https://docs.github.com/en/pages/configuring-a-custom-domain-for-your-github-pages-site/troubleshooting-custom-domains-and-github-pages#cname-errors

> CNAME errors
>
> If you are publishing from a custom GitHub Actions workflow, any CNAME file is ignored and is not required.
> If you are publishing from a branch, custom domains are stored in a CNAME file in the root of your publishing source.