Update ci.yml for codecov v4

[JeffFessler]

Hopefully addresses #228

[JeffFessler]

I have no idea why julia 1.6 for macOS failed.

[dkarrasch]

Could you please rebase onto current master? I relaxed the CI configuration a bit. I suspect that this works just fine, but would like to see some confirmation.

[JeffFessler]

Sadly I don't know how to do that, and I bet it will be faster for you to just close this PR and make a new PR than to teach me how! And that's OK. Is there is a github button I am overlooking for it? I tried to RTFM:
https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/incorporating-changes-from-a-pull-request/about-pull-request-merges#rebase-and-merge-your-commits

[dkarrasch]

Indeed, I'm also missing that "rebase" button that I'm used to from the julia repo. @fredrikekre Do you know where to set this up?

I'll still share what I learnt from others in the community. After you updated your local master branch, you switch to the PR branch and then do

git pull --rebase origin master

to pull from master and rebase the current branch. Afterwards, you can resolve merge conflicts if necessary and then

git push --force

[dkarrasch]

I think I found the button.

[dkarrasch]

Seems like it still doesn't solve the problem? I'm seeing

Upload failed: {"detail":"You do not have permission to perform this action."}

in the CI / Julia1 - ubuntu-latest run.

[fredrikekre]

That is because this PR is from a fork and the secret is not available.