Fix json-serve script

package.json

     "build": "react-scripts build",
     "test": "react-scripts test",
     "eject": "react-scripts eject",
-    "json-serve": "json-server ./db/randomData.js --port=4000"
+    "json-serve": "json-server ./db/db.js --port=4000"
   },
   "eslintConfig": {
     "extends": [