Error in pre_release() if using it on a private repository

[maelle]

Admittedly quite a niche use case :sweat_smile:

→ Opening draft pull request with contents from cran-comments.md.
Erreur dans gh_process_response(raw) : 
GitHub API error (422): 
Message: Draft pull requests are not supported in this repository.
Read more at https://docs.github.com/rest/reference/pulls#create-a-pull-request
Type .Last.error.trace to see where the error occurred

[krlmlr]

I don't mind removing draft = FALSE, it will become inconsequential with #31 and #262.

[krlmlr]

We no longer use draft = FALSE .