accidental typo fixed

Author: Sruthi235

backend/app.py

@@ -11,7 +11,7 @@
 from flask_socketio import SocketIO, emit
 from flask_jwt_extended import (
     JWTManager, create_access_token, jwt_required, 
-    get_jwt_identity, set_access_cookies, unset_jwt_cookiesS
+    get_jwt_identity, set_access_cookies, unset_jwt_cookies
 )
 from flask_limiter import Limiter
 from flask_limiter.errors import RateLimitExceeded