docs: adjust mermaid diagram page with admonition

[adamaltman]

What/Why/How?

Removes rendering the diagrams by default. Explains how to render them, and adds an admonition explaining it uses a microservice we host in AWS.

Reference

Closes https://github.com/Redocly/marketing-site-portal/issues/880

Security

• [x] Security impact of change has been considered
• [x] Code follows company security practices and guidelines