Remove spurious script tag.

The js/models/store.js file referenced here has not (yet?) appeared in the getting started guide, and does not appear in the associated diff for this step:

https://github.com/emberjs/quickstart-code-sample/commit/60feb5f369c8eecd9df3f561fbd01595353ce803

Thus, it should probably be removed from the code listing, since it'll just 404.