GH warnings when running get-releasenote action

[mjpieters]

When you run the aio-libs/get-releasenote@v1.4.5 action, Github adds this warning (repeated three times):

Warning: The set-output command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

As the linked blog page states, the deprecation has been postponed but I'm assuming it's not a stay of execution.

To fix the warning, replace printing with appending to the os.environ.get("GITHUB_OUTPUT") filename, if it exists.

[asvetlov]

Thanks for the reminder; I'll prepare a fix