update checkout versions

Author: fangohr

.github/workflows/deploy.yml

@@ -11,7 +11,7 @@ jobs:
   docker-build-and-deploy:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
 
     - name: Set up Docker Buildx
       uses: docker/setup-buildx-action@v1

.github/workflows/nbval.yml

@@ -9,7 +9,7 @@ jobs:
   docker-build-and-nbval:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
 
     - name: Set up Docker Buildx
       uses: docker/setup-buildx-action@v1

.github/workflows/stage.yml

@@ -9,7 +9,7 @@ jobs:
   docker-build-and-stage:
     runs-on: ubuntu-latest
     steps:
-    - uses: actions/checkout@v2
+    - uses: actions/checkout@v4
 
     - name: Set up Docker Buildx
       uses: docker/setup-buildx-action@v1