Remove backticks from Mermaid diagrams on Documentation deployments page

What does this MR do and why?

Removes backticks from Mermaid diagrams on this page: https://docs.gitlab.com/ee/development/documentation/site_architecture/deployment_process.html

These throw errors in Mermaid 10.4.0 that were not present in Mermaid 9.4.3.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

• Before: https://docs.gitlab.com/ee/development/documentation/site_architecture/deployment_process.html
• After: https://main-ee-131938.docs.gitlab-review.app/ee/development/documentation/site_architecture/deployment_process.html

Before	After

How to set up and validate locally

(Validate on the Docs site)

1. Compile the docs site
2. Visit this page: http://localhost:3000/development/documentation/site_architecture/deployment_process.html
3. Verify the three Mermaid charts render without errors.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.