Add documentation for new Snippet repository storage move API

What does this MR do?

This MR adds the documentation for the newly introduced endpoints in the REST API to move snippet repository storage.

Related to #218997 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides- [ ] Separation of EE specific content