fix username in ssh

.github/workflows/deploy.yaml

@@ -30,7 +30,7 @@ jobs:
         uses: appleboy/ssh-action@v1
         with:
           host: ${{ secrets.VPS_HOST }}
-          username: app
+          username: ${{ secrets.VPS_USERNAME }}
           key: ${{ secrets.VPS_SSH_KEY }}
           script: |
             mkdir -p /home/nullplate/deflock/backend/dist