audio/player: Fix properties being marked as experimental

The media API is considered stable so these properties shall not have
experimental flags set.
diff --git a/profiles/audio/player.c b/profiles/audio/player.c
index 4736396..465bff5 100644
--- a/profiles/audio/player.c
+++ b/profiles/audio/player.c
@@ -1102,10 +1102,8 @@
 };
 
 static const GDBusPropertyTable media_folder_properties[] = {
-	{ "Name", "s", get_folder_name, NULL, folder_name_exists,
-					G_DBUS_PROPERTY_FLAG_EXPERIMENTAL },
-	{ "NumberOfItems", "u", get_items, NULL, items_exists,
-					G_DBUS_PROPERTY_FLAG_EXPERIMENTAL },
+	{ "Name", "s", get_folder_name, NULL, folder_name_exists },
+	{ "NumberOfItems", "u", get_items, NULL, items_exists },
 	{ }
 };