gh-pages CI job on PRs is erroring out

[rgommers]

The preview CI job seems to have an issue right now, from this log from gh-464:

Run git push "***github.com/data-apis/array-api.git"
remote: Permission to data-apis/array-api.git denied to github-actions[bot].
fatal: unable to access 'https://github.com/data-apis/array-api.git/': The requested URL returned error: 403
Error: Process completed with exit code 128.

It seems to be misconfigured, so it works for PRs made from a branch within this repo, but fails when it's from a fork. We shouldn't use the former anyway, @kgryte can you please send PRs from your fork and clean up the many branches in this repo?

[jakirkham]

Maybe a token expired and needs to be regenerated/readded?

[rgommers]

Fixed now. There were two problems:

1. The publish workflow was running on branches other than main
2. The preview CI job on CircleCI was not triggering on forks.

To fix (2), I had to toggle this button:

[rgommers]

Third issue is that the permissions issue reported above is still happening on main.

[rgommers]

That last issue fixed in commit 792f11e.