Move security partners to Integrations page

What does this MR do and why?

• Moves and redirects the Security partners page to Integrate with GitLab: Security partners
• Alphabetizes all entries on the list

Related MR

• gitlab-docs!4018 (merged) to delete the nav entry for the Security partners page

Screenshots or screen recordings

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

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

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.