[katsugtgz]

Updates actions/checkout from v1 and v3 to v7, and actions/setup-python from v4 to v7 in .github/workflows/lint.yml.

Compatibility notes:

• setup-python v7 keeps python-version optional; the vint job sets no inputs today, so behavior is unchanged.
• checkout v5 and later block fork checkouts by default for pull_request_target and workflow_run triggers. This workflow uses push and pull_request only.

Validation: the workflow file parses as YAML, and no checkout@v1, checkout@v3, or setup-python@v4 references remain.

Scope: one workflow file, version refs only.