Don't escape html entities in InlineDiffMarkdownMarker

What does this MR do?

It does not escape htmlentities in InlineDiffMarkdownMarker because this class is used only when creating a system note for the change of title and as the name suggests it is markdown and goes through markdown pipeline afterwards.

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

Why was this MR needed?

When the line was html escaped it caused that the text inside code block was rendered incorrectly when it contained html entities. These entities were first escaped in the InlineDiffMarkdownMarker (StringRangeMarker) and then they were rendered as entities because they were inside the code block.

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

What are the relevant issue numbers?

Closes #36041 (closed)