Remove loadHTMLFixture usage in `spec/frontend/notes/`

This MR aims to solve #405323 (closed)

I have replaced references to loadHTMLFixture in the following places:

spec/frontend/notes/deprecated_notes_spec.js:39: loadHTMLFixture(fixture);

spec/frontend/notes/deprecated_notes_spec.js:674: loadHTMLFixture('commit/show.html');