[FIX] gh-pages branch: CircleCI error

[zhao-cy]

There is a branch called gh-pages, and when I merge a PR or push a commit to main, (not necessary after other circleci workflows and pkgdown finishes deployes,) this branch has an automatic new commit which triggers circleci --> error (only has develR).

Even with this error, we can still get green checkmark for the merging PR to main.

Can I delete this branch?