Render inline code in merge request sticky header

What does this MR do and why?

A merge request title can contain inline code written with backticks (e.g. code). The sticky header that appears when you scroll down showed this title as plain text, so the backticks were not rendered as code markup. This changes the sticky header to render the title's markdown, so inline code now shows as code markup, matching the main header and the way work items already behave. It also keeps that markup when you toggle the merge request between draft and ready, which previously reset the title back to plain text.

References

There is no linked issue for this change.

Screenshots or screen recordings

Before	After
Sticky header
Initial header, non-sticky toggling to Draft

How to set up and validate locally

1. Create or edit a merge request whose title contains inline code with backticks, for example: Fix `foo` bar.
2. Open the merge request page.
3. Scroll down until the sticky header appears at the top of the page.
4. Confirm the inline code renders as code markup in the sticky header, matching the main header.
5. Toggle the merge request between draft and ready, then confirm the code markup is still shown in both the main header and the sticky header.

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