Add snippet on how to export a project to GitLab Rails Console Cheat Sheet

What does this MR do?

This merge request updates the GitLab Rails Console Cheat Sheet to include a snippet that demonstrates how to export a project. This snippet was helpful in a ticket. I'm adding it here as I suspect it will be useful to others.

Screenshots (strongly suggested)

Does this MR meet the acceptance criteria?

Conformity

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

Availability and Testing

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team