Remove Talkback announcement of new widget added.

Per guidelines, a disruptive announcement should not be used. As
TYPE_WINDOW_STATE_CHANGED events will also not always be announced
anymore, this change removes the announcement from the widget addition.
The decision to remove the announcement instead of using a label on
the user interface was made as this is a temporary state that isn't
a permanent attribute of the associated View.

Fixes: 398744371
Test: manual - verified no announcement on widget addition
Flag: EXEMPT bugfix
Change-Id: If5159275b99396bc5d34ac341dcea6d7580e848f