Turn bubble any message on by default

Flipping this on by default means that MessageStyle notifs with enough
info to bubble will show a "bubble" option in the notif longpress menu.

Bug: 145763712
Test: manual - get a hangouts message, longpress on it, see bubble option
Change-Id: Ied9e5dba58b2d717a43a687a3900391dd8fc1646