MarkupHelper#link_to_html should produce single link when possible
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The following discussion from !18014 should be addressed:
- [ ] @leipert started a [discussion](https://gitlab.com/gitlab-org/gitlab/merge_requests/18014#note_231983318): (+4 comments)
> @harishsr This will actually render two links. Shouldn't it be:
>
> ```html
> <a href="/foo">
> <gl-emoji title="open book" data-name="book" data-unicode-version="6.0">📖</gl-emoji> Book
> </a>
> ```
>
> instead?
issue