ci: update checkout and setup-python to current versions

[katsugtgz]

Updates the test workflow to the current action versions.

Changes:

• actions/checkout@v3 -> pinned to the v7.0.1 commit
• actions/setup-python@v3 -> pinned to the v7.0.0 commit
• adds a least-privilege permissions block (contents: read)

The workflow sets only python-version on setup-python, an input unchanged in v7, so the bump is drop-in.

Validation:

• YAML parses after the change
• yamllint run: only pre-existing trailing-space warnings remain

Scope: .github/workflows/test.yml only. docs.yml and release.yml still reference v3 and are left for a separate change if wanted.

Commit author katsugtgz, unsigned. Fork workflow runs need maintainer approval.

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