Dialer: Don't prompt to send a message to sensitive numbers

* When calling a number but hanging up, you get a prompt "Send a message"
* For a sensitive number that doesn't make sense for two reasons
  a) The message possible wouldn't get received there (most likely)
  b) The message would then show up in the messaging app - which is not
     really desired either

Change-Id: Ic6450d5a44ba97a4da085adb1da0275477bb14fc