Update README.md

Co-authored-by: Jagdish Prajapati <jagadishdrp@gmail.com>

Author: adityak-06

README.md

@@ -66,7 +66,7 @@ leetcode-ranking/
 │── frontend/        # UI (HTML, CSS, JS)
 │── data/            # Stored user data
 │── scripts/         # Automation scripts
-│── server.js        # Backend server
+│── server.js        # Express server
 │── package.json
 ```