Update docker/setup-buildx-action action to v4

Author: renovate[bot]

.github/workflows/webapp-dev.yml

@@ -36,7 +36,7 @@ jobs:
         path: docker-netbootxyz
 
     - name: Set up Docker Buildx
-      uses: docker/setup-buildx-action@v3
+      uses: docker/setup-buildx-action@v4
 
     - name: Login to the GitHub Container Registry
       uses: docker/login-action@v3