Upgrade GitHub Actions and refine dependency install

Updated GitHub Actions workflow to use newer action versions and improved dependency installation.

Author: bmoscon

.github/workflows/tests.yml

@@ -11,16 +11,16 @@ jobs:
         python-version: [3.11, 3.12, 3.13]
 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v5
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: actions/setup-python@v6
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install dependencies
         run: |
           python -m pip install --upgrade pip
           pip install flake8 pytest requests sortedcontainers
-          python setup.py install
+          pip install
       - name: Test with pytest
         run: |
           pytest tests/