Settings: remove Bluetooth related text from DNS-dialog

 * String ´bluetooth_select_a2dp_codec_type_help_info´
   is set on the ´preference_widget_dialog_summary´-dialog
   by default.

Test: make Settings, visual observation
Signed-off-by: Timi Rautamäki <timi.rautamaki@gmail.com>
Change-Id: I6d403f231797bcf5b10bf726cca4e128f4c517ea