qt: reduce playlist delegate vertical padding

Although having excessive padding makes it possible
to interact with the delegate using touch control
easier, it also causes the playlist to show less
items at once.

VLC is primarily a desktop application, although
we should care about touch support, we should not
optimize the design for touch.

Reducing the vertical padding from 6dp to 2dp seems
to be good compromise. It is still very much possible
to use touch, but also looks okay for a desktop
application.

modules/gui/qt/playlist/qml/PlaylistDelegate.qml

@@ -64,7 +64,7 @@ T.Control {
 
     hoverEnabled: true
 
-    verticalPadding: VLCStyle.playlistDelegate_verticalPadding
+    verticalPadding: VLCStyle.margin_xxxsmall
 
     leftPadding: VLCStyle.margin_normal
 

modules/gui/qt/style/VLCStyle.qml

@@ -232,8 +232,6 @@ QtObject {
 
     readonly property int artistBanner_height: MainCtx.dp(200, scale)
 
-    readonly property int playlistDelegate_verticalPadding: MainCtx.dp(6, scale)
-
     //global application size, updated by the root widget
     property int appWidth: 0
     property int appHeight: 0