Update actions/checkout action to v4

Author: renovate[bot]

.github/workflows/docker_image_ci.yml

@@ -6,7 +6,7 @@ jobs:
   build:
     runs-on: ubuntu-latest 
     steps:
-      - uses: actions/checkout@v2
+      - uses: actions/checkout@v4
       - name: Build the docker-compose stack
         run: docker-compose -f docker/docker-compose.yml up --build --force-recreate