chore: bump deprecated GitHub Actions to Node20 majors

Update pinned action versions in .github/workflows/test.yml to eliminate
Node16 deprecation warnings emitted at runtime:

- actions/checkout@v3 → actions/checkout@v4 (Node20)
- actions/setup-python@v4 → actions/setup-python@v5 (Node20)

GitHub deprecated Node16-based actions; checkout@v3 and setup-python@v4
both run on Node16 and emit deprecation warnings, violating the
Zero-Warnings policy. No behavioral change to job steps.

Co-Authored-By: Claude <noreply@anthropic.com>

Author: sempi

.github/workflows/test.yml

@@ -11,10 +11,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Check out repository
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
 
       - name: Set up Python
-        uses: actions/setup-python@v4
+        uses: actions/setup-python@v5
         with:
           python-version: "3.12"