Replace deprecated command with environment file

[jongwooo]

Description

Resolve #320

Update .github/workflows/ci.yml to use environment file instead of deprecated set-output command.
For more information, see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

I found the workflow file that use set-output command through the following command:

$ find . -name '*.yml' -o -name '*.yaml' | xargs egrep '\bset-output\b'

AS-IS

echo "::set-output name=dir::$(pip cache dir)"

TO-BE

echo "dir=$(pip cache dir)" >> $GITHUB_OUTPUT

[alxmrs]

This looks pretty good to me. Can you make sure that the 3.8 CI passes before me merge this?

[jongwooo]

@alxmrs I've tried force-push. If that fails, I'll change this PR to draft and try to fix it😅