🔒 pin tests.yml actions to commit SHAs (#721)

Author: paulinebm

.github/workflows/tests.yml

@@ -16,9 +16,9 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout code
-        uses: actions/checkout@v4
+        uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd  # v6.0.2
       - name: Setup Python environment
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@a26af69be951a213d495a4c3e4e4022e16d87065  # v5
         with:
           python-version: 3.10.10
       - name: Install dependencies