Remove QtMultimedia import when not needed

src/FlightDisplay/FlightDisplayView.qml

@@ -14,7 +14,6 @@ import QtQuick.Controls.Styles  1.4
 import QtQuick.Dialogs          1.2
 import QtLocation               5.3
 import QtPositioning            5.3
-import QtMultimedia             5.5
 import QtQuick.Layouts          1.2
 import QtQuick.Window           2.2
 import QtQml.Models             2.1

src/ui/preferences/GeneralSettings.qml

@@ -12,7 +12,6 @@ import QtQuick                  2.3
 import QtQuick.Controls         1.2
 import QtQuick.Controls.Styles  1.4
 import QtQuick.Dialogs          1.2
-import QtMultimedia             5.5
 import QtQuick.Layouts          1.2
 
 import QGroundControl                       1.0