LibGUI: Remove 2px of vertical space around FilePicker common places

The extra margin is not needed with the new "Tray" look. :^)

Userland/Libraries/LibGUI/FilePickerDialog.gml

@@ -24,7 +24,7 @@
             fill_with_background_color: true
 
             layout: @GUI::VerticalBoxLayout {
-                margins: [2, 4, 2, 4]
+                margins: [2, 2, 2, 2]
                 spacing: 0
             }
         }