Markdown rendering of mermaid inside of detail view mangles the html

Summary

When using the mermaid graphs inside of the detail view, GitLab markdown does not correctly render the html, leaving the graph in an undecipherable state.

Steps to reproduce

Click this to see a poor rendering

This is some text

graph LR
A --> B
B --> C

This is more text.

What is the expected correct behavior?

I would expect the above, when expanded to look like this:

This is some text

graph LR
A --> B
B --> C

This is more text.

Example Code

This code example is not entirely complex either:

This is some text
```mermaid
graph LR
A --> B
B --> C
```
This is more text.