Bump docker/setup-buildx-action from 3 to 4 (#3389)

Author: dependabot[bot]

.github/workflows/continuous_integration.yml

@@ -30,7 +30,7 @@ jobs:
       run: mkdir secrets && echo -n "openslides" > secrets/postgres_password
 
     - name: Setup Docker Buildx
-      uses: docker/setup-buildx-action@v3
+      uses: docker/setup-buildx-action@v4
       with:
         version: latest