- Update the GitHub Actions workflows to their latest versions.
- Replace the usage of the deprecated `set-output` command with the
new recommended way to set the output.
- Format the YAML files.
This commit is a revert of 53e52d2c4b.
Partially done because the workaround is no longer needed, partially
because macOS images have begun to fail after a new image rollout with
bumped NuGet versions.