Remove call preventing video calls when TTY enabled.

This code was originally put in Telecom, and it really doesn't belong
there.  There is no reason why we should impose a telephony restriction
in Telecom.
Further, the code which generates a Toast in this scenario actually causes
Telecom to crash.
Moving this check to Telephony instead.

Bug: 20090652
Change-Id: I777c0a8bfad59f9aea9abc6680f46284548912c4