fix: use `GITHUB_ACTOR` in `git config`

[vil02]

Description of Change

Same as TheAlgorithms/Rust#647 - it contains the description of the problem, which this PR solves.

Checklist

• [x] Added description of change
• [x] PR title follows semantic commit guidelines
• [x] Search previous suggestions before making a new one, as yours may be a duplicate.
• [x] I acknowledge that all my contributions will be made under the project's license.

Notes: Properly evaluates the GITHUB_ACTOR variable.

[github-actions[bot]]

This pull request has been automatically marked as abandoned because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[vil02]

Please don't close or make it approved.