RESTRICT AUTOMERGE Update string

1. Replace "An untrusted Bluetooth device" to "A Bluetooth device".
2. Replace "Deny" to "Don't allow"

https://docs.google.com/document/d/18bVSIAyX4MNpNeCvxqyZu7CXcBUcdV0pnh-gzVprjqU/edit?ts=60709637

Bug: 167403112
Test: send intent to test right prompts message is pop up.
make -j42 RunSettingsRoboTests

Change-Id: I38da15d4b1fb08671f6352458cbf3f735b4083bc
(cherry picked from commit 38fc9a91)