Airlines no Longer need to warn Boarding Passengers about the Galaxy Note 7

Because it's now safe?

Not particularly

The Department of Transportation has lifted a requirement that airlines notify passengers that the recalled Samsung Galaxy Note 7 is a prohibited flight risk. 

This is according to a press release by the Federal Aviation Administration. 

This is not to say that the phone is now allowed on flights, just that the DoT feel there has been sufficient warning on dangers of the phone to make it relatively safe to not announce it before takeoff.

Whether individual Airlines themselves will go with the recommendation of the DoT remains to be seen as it is very possible that airlines will continue to make the announcement for the safety of their passengers.

In a statement following the FAA's announcement, Samsung says that over 96 percent of Note 7 devices have been returned so far and with man measures being taken to make the phone positively unattractive to users, it seems that the 4% is almost negligible.