Change link for "My Organization is Ready to Join" to point to membership application's "Ready to Join" page in WGs list

As requested in eclipsefdn/it/websites/membership.eclipse.org#656 (closed), we need to update the button to link to the newly created https://membership.eclipse.org/application/ready-to-join page.

This change must only go live once the ready-to-join page is live on production.