Set fetchMock.config.fallbackToNetwork for Storybook (#7369)

GitOrigin-RevId: df957893c8495c582d721716daa20030deb02f72

services/web/frontend/stories/hooks/use-fetch-mock.js

@@ -1,5 +1,6 @@
 import { useEffect } from 'react'
 import fetchMock from 'fetch-mock'
+fetchMock.config.fallbackToNetwork = true
 
 /**
  * Run callback to mock fetch routes, call restore() when unmounted