Show scroll indicator for longer time

src/QmlControls/QGCFlickableHorizontalIndicator.qml

@@ -33,7 +33,7 @@ Rectangle {
         properties:    "opacity"
         from:          1.0
         to:            0.0
-        duration:      1000
+        duration:      3000
         easing.type:   Easing.InQuint
     }
 }

src/QmlControls/QGCFlickableVerticalIndicator.qml

@@ -33,7 +33,7 @@ Rectangle {
         properties:    "opacity"
         from:          1.0
         to:            0.0
-        duration:      1000
+        duration:      3000
         easing.type:   Easing.InQuint
     }
 }