infra: fix bump_license_year.yml not adding year to commit message

[Vyom-Yadav]

Source: https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#setting-an-environment-variable

Proof of working: https://github.com/Vyom-Yadav/actions-test/commit/8ae3f4490e16f3bbba5f252f96b03e15198e8122