Get rid of code to allow bypassing short-code confirmation dialog.

It was allowed based on permission SEND_RESPOND_VIA_MESSAGE but that 
permission is used for other purposes and should not be used for this.
No app seems to require the ability to bypass the check so removing the 
check altogether. If that ability is needed, a separate permission 
should be added for it.

Bug: 23766433
Change-Id: Ie93f75725c316b39684cf740dfd161c084c60181