Fix description flash with newline differences (HTML entities)

What does this MR do?

• Fix description flash with newline differences

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

When grabbed from innerHTML

<p dir="auto">foo
bar</p>

From the API (HTML entities)

<p dir="auto">foo&#x000A;bar</p>

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References

• Render Description Realtime 🎉, https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/10865
• Refactored issue realtime elements, https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11242

Why was this MR needed?

• The issue description was flashing on page load

Does this MR meet the acceptance criteria?

• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• 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 #33265 (closed)