Remove useless attachToDocument usage in spec/frontend/notes

What does this MR do?

As described in &2419 (closed), cleans up our Jest tests from unnecessary attachToDocument usage

Involved specs

• spec/frontend/notes/components/comment_form_spec.js
• spec/frontend/notes/components/discussion_jump_to_next_button_spec.js
• spec/frontend/notes/components/discussion_notes_spec.js
• spec/frontend/notes/components/note_app_spec.js
• spec/frontend/notes/components/note_edited_text_spec.js

Conformity

• Merge request performance guidelines
• Style guides

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.

Closes: #196759 (closed)