fix checkout

Author: alejoe91

.github/workflows/test_containers_singularity.yml

@@ -16,7 +16,7 @@ jobs:
         # "macos-latest", "windows-latest"
         os: ["ubuntu-latest", ]
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v3
 
       - uses: actions/setup-python@v4
         with: