All docs pages have the same comments

There's something's wrong with Disqus, every doc page has the same comments.

We load disqus in feedback.html and then from disqus.js.

We define the disqus identifier for each page with:

this.page.identifier = '<%= @item[:disqus_identifier] %>';

In !1312 (merged), we changed the location of the javascript files, and that resulted in all pages having the same identifier:

  this.page.identifier = 'https://docs.gitlab.com/assets/javascripts/disqus.html';

TL;DR: We have defined the Disqus snippet in an immutable file (assets/javascripts/disqus.js), and the code to extract the unique Disqus identifier takes into account the name of the file. It used to be embedded right into each HTML page.