Mermaid diagrams for GitLab blog not rendered

Summary

In many of our blog posts in https://about.gitlab.com/blog, we use mermaid diagrams. These diagrams are no longer rendered properly. Instead, we just display the mermaid code.

Example Blogs

Some examples include

1. https://about.gitlab.com/blog/2020/07/28/container-security-in-gitlab/
2. https://about.gitlab.com/blog/2021/09/08/write-vulnerability-detection-rules
3. https://about.gitlab.com/blog/2023/06/20/contributions-to-latest-git-release/

What is the current bug behavior?

mermaid semgments are not rendered, instead the code is just displayed.

What is the expected correct behavior?

We should see the rendered diagram instead of the code.

Relevant logs and/or screenshots

Below is what we currently see

sequenceDiagram
    actor user
    participant Gitlab UI
    participant p as Praefect
    participant g0 as Gitaly (primary)
    participant git as Git
    user->>Gitlab UI: mirror my repository
    Gitlab UI->>p: FetchRemote
    activate p
    p->>g0: FetchRemote
    activate git
    g0->>git: fetch-remote
    git->>g0: vote on refs/heads/branch1 update
    g0->>p: vote on refs/heads/branch1 update
    git->>g0: vote on refs/heads/branch2 update
    g0->>p: vote on refs/heads/branch2 update
    git->>g0: vote on refs/heads/branch3 update
    g0->>p: vote on refs/heads/branch3 update
    deactivate git
    note over p: vote succeeds
    p->>Gitlab UI: success
    deactivate p

Instead what we would like to see is

sequenceDiagram
    actor user
    participant Gitlab UI
    participant p as Praefect
    participant g0 as Gitaly (primary)
    participant git as Git
    user->>Gitlab UI: mirror my repository
    Gitlab UI->>p: FetchRemote
    activate p
    p->>g0: FetchRemote
    activate git
    g0->>git: fetch-remote
    git->>g0: vote on refs/heads/branch1 update
    g0->>p: vote on refs/heads/branch1 update
    git->>g0: vote on refs/heads/branch2 update
    g0->>p: vote on refs/heads/branch2 update
    git->>g0: vote on refs/heads/branch3 update
    g0->>p: vote on refs/heads/branch3 update
    deactivate git
    note over p: vote succeeds
    p->>Gitlab UI: success
    deactivate p

Output of checks