Fix error publishing docs

[dwickern]

Fixes #1597
Supersedes #1618

I'm opening this PR from this repository instead of my fork. Hopefully that will fix the permissions issue.

[dwickern]

Well, it's a different error at least

[error] remote: error: GH006: Protected branch update failed for refs/heads/gh-pages.        
[error] remote: error: Required status check "typesafe-cla-validator" is expected.        
[error] To https://github.com/sbt/sbt-native-packager
[error]  ! [remote rejected]   gh-pages -> gh-pages (protected branch hook declined)
[error] error: failed to push some refs to 'https://github.com/sbt/sbt-native-packager'
[error] Nonzero exit code (1) running git.
[error] (ghpagesPushSite) Nonzero exit code (1) running git.

[dwickern]

Successfully published! 🎉 https://www.scala-sbt.org/sbt-native-packager/

I used b6c9142 to test publishing from this PR. I'll drop the commit before merging. Importantly, I had to open this PR from the main repo and not my fork in order for Github Actions to have write permission. You can see the permissions granted by GITHUB_TOKEN in the "Set up job" phase of the Github Actions job.

I made the following changes outside of this PR:

• Removed branch protection (e.g. must sign CLA) from gh-pages branch
• Removed KNOWN_HOSTS and SSH_KEY secrets (in order to clean up the now unused secrets)

[muuki88]

Is there a reason to use this old version?

[dwickern]

No reason, I just copied it from release.yml

[muuki88]

Amazing work 🙏💪thanks a lot