Minor update to GH actions.

Author: applebyter

.github/workflows/app.yml

@@ -11,26 +11,24 @@ jobs:
     steps:
 
     - name: Checkout
-      uses: actions/checkout@v2
+      uses: actions/checkout@v4
 
     - name: Set up Docker Buildx
-      uses: docker/setup-buildx-action@v1
+      uses: docker/setup-buildx-action@v3
 
     - name: Log in to the Container registry
-      uses: docker/login-action@v1
+      uses: docker/login-action@v3
       with:
         registry: ghcr.io
         username: ${{ github.actor }}
         password: ${{ secrets.GITHUB_TOKEN }}
 
     - name: Build and push Docker image
-      uses: docker/build-push-action@v2
+      uses: docker/build-push-action@v6
       with:
         context: .
         file: Dockerfile
         push: true
         platforms: linux/arm64,linux/arm/v8,linux/amd64
         tags: |
           ghcr.io/csse6400/csse6400-cloud-testing:latest
-    
-