Use an unofficial setup-python action that still works with 2.7

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

Author: andersk

.github/workflows/tests-and-lint.yml

@@ -17,7 +17,7 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - name: Set up Python ${{ matrix.python-version }}
-        uses: actions/setup-python@v2
+        uses: LizardByte/setup-python-action@v2024.919.163656
         with:
           python-version: ${{ matrix.python-version }}
       - name: Install Dependencies