Edit broken http_mocking.md doc Smocker link to current one

What does this MR do and why?

Edits broken Smocker getting started link to current one

Screenshots or screen recordings

current link in repo:

new link:

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.

• Commits include Changelog: trailer
• I have evaluated the MR acceptance checklist for this MR.