Merge branch '23661-lacking-padding-on-syntax-highlight-blocks-in-diff-comments' into 'master'

Resolve "Lacking padding on syntax highlight blocks in diff comments"

## What does this MR do?

Enforces horizontal padding on highlight block.

## Are there points in the code the reviewer needs to double check?

## Why was this MR needed?

There was no horizontal padding on diff comment highlight blocks.

## Screenshots (if relevant)

![Screen_Shot_2016-10-23_at_01.48.10](/uploads/6d7a426c0856e8787b63b2c02672298a/Screen_Shot_2016-10-23_at_01.48.10.png)

## Does this MR meet the acceptance criteria?

- [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG.md) entry added
- [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
- [ ] API support added
- Tests
  - [ ] Added for this feature/bug
  - [ ] All builds are passing
- [ ] Conform by the [merge request performance guides](http://docs.gitlab.com/ce/development/merge_request_performance_guidelines.html)
- [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [ ] Branch has no merge conflicts with `master` (if it does - rebase it please)
- [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)

## What are the relevant issue numbers?


Closes #23661

See merge request !7062

app/views/projects/diffs/_parallel_view.html.haml

 / Side-by-side diff view
-%div.text-file.diff-wrap-lines.code.file-content.js-syntax-highlight{ data: diff_view_data }
+%div.text-file.diff-wrap-lines.code.js-syntax-highlight{ data: diff_view_data }
   %table
     - last_line = 0
     - diff_file.parallel_diff_lines.each do |line|