correct python version

Author: alejoe91

.github/workflows/test_containers_singularity.yml

@@ -16,9 +16,11 @@ jobs:
         # "macos-latest", "windows-latest"
         os: ["ubuntu-latest", ]
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-python@v4
         with:
-          python-version: "3.9"
+          python-version: '3.9'
 
       - uses: eWaterCycle/setup-singularity@v7
         with: