.github: Update docker/build-push-action to v6

Author: krnowak

.github/workflows/docker.yml

@@ -49,7 +49,7 @@ jobs:
         password: ${{ secrets.GITHUB_TOKEN }}
 
     - name: Build and push
-      uses: docker/build-push-action@v5
+      uses: docker/build-push-action@v6
       with:
         context: .
         push: true