Remove rogue scrollbars from some issue comments

What does this MR do?

Remove rogue scrollbars that appear in macOS Firefox, Windows IE11 and Edge for some comments*.

*Some comments is defined by a comment with some inline elements like code snippets and there is enough content to wrap to the next line

Here is a barebones demo that reproduces the issue: https://jsfiddle.net/jn5zsvju/

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

.note-body

• See ./app/views/projects/notes/_notes.html.haml -> projects/notes/note
• Issue page
• MR page
• Commit page, /group/project/commit/:sha1

cc @annabeldunstone

Why was this MR needed?

Screenshots (if relevant)

Before

After

Test comment source

Yes, me too, +1ed.. My `group.gitlab.io/project` works fine, `sub.domain1` with CNAME `group.gitlab.io` works fine, but `sub.domain2` shows gitlab 404 error.

`awefaewfaewfaewfewfkjhewfaewlfjakew;lfjawflkjlwfkjlfejwkalfjkawfelkjwafjlkfjfkfeajkkjlewfalkjewfajlkfewakjewfakjlewfakjfewakjlfewajlkewafjlkfewakjlfewakjlafewjlkfaewkjlfewajlkfewakjfewakjwajekf`

foo | bar | baz
--- | --- | ---
qux | garply | waldooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo

Does this MR meet the acceptance criteria?

• Changelog entry added
• Tests
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #25989 (closed)