Remove Feature Code Admin -> Contact Mgr Speeddial as destination

raised by smmc in discourse:
https://community.freepbx.org/t/sent-to-invalid-extension-but-no-invalid-handler-when-using-contact-manager-speed-dials-as-destination/64988

It is possible to set a call destination of Feature Code Admin, Contact Manager Speeddials. But when the call goes to this destination it fails. I can see no practical purpose for being allowed to set this as a destination, and recommend that this option be removed.

It's possible that it was added for ticket FREEPBX-8203, which was a request that individual contact manager entries be usable as a destination, but it's not working.