Mermaid Output in doxygen not displaying correctly

[Ulrond]

• When doxygen outputs html there's a bug in the render that it's not generated correctly, this is a known bug with doxygen.
• We need to fix the issue in the github code, or check that someone else hasn't fixed it.
• raise a ticket on doxygen github, and submit our change
• In the meantime until the uprevision, we need to keep applying the patch to the code.
• It may be rendered correctly if we followed the same fix that was applied for plantUML.

doxygen/doxygen#9950