Update Fullstory snippet to pull from CDN

Fullstory updated their regular snippet some months back; the snippet in this module should be updated.

As of October 30th, 2019, FullStory is now hosting the FullStory script (fs.js) on Google’s Content Delivery Network (CDN) in an effort to improve script load times for our customers’ clients.[...]

This update included a new flag in the code, highlighted below:

<script>
window['_fs_debug'] = false;
window['_fs_host'] = 'fullstory.com';
window['_fs_script'] = 'edge.fullstory.com/s/fs.js';
...
</script>