update ci.yaml

.github/workflows/ci.yaml

@@ -11,7 +11,7 @@ jobs:
       - name: login to dockerhub
         uses: docker/login-action@v3.6.0
         with:
-          username: ${{ vars.DOCKERHUB_USERNAME }}
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
           password: ${{ secrets.DOCKERHUB_TOKEN }}
 
       - name: Build and push