modify _title.haml to fix colors on new merge request page

What does this MR do?

Modifies the partial _title.haml to use the help_block class for the element that needed to use the secondary colors instead of the default black text color.

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

I have solved the issue by modifying the haml file, but I would appreciate any guidance the reviewer could give me regarding if this is the proper way of solving this issue through other means like modifying css or the layout of the haml file.

Why was this MR needed?

It resolves the issue mentioned in issue 39863.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered

What are the relevant issue numbers?

Fixes #39863 (closed).