Fix test login script to work with test register script

backend/requests/login.sh

@@ -1 +1 @@
-curl -X POST -H "Content-Type: application/json" -d '{"username": "a", "password": "c"}' localhost:8000/api/login
+curl -X POST -H "Content-Type: application/json" -d '{"username": "roflin", "password": "oreokoekje123"}' localhost:8000/api/login