Fix `DisplayServer.has_feature()` claiming X11 has native icon support

Native icons are not supported by the X11 DisplayServer, unlike
Windows and macOS.

platform/linuxbsd/display_server_x11.cpp

@@ -126,7 +126,7 @@ bool DisplayServerX11::has_feature(Feature p_feature) const {
 		case FEATURE_WINDOW_TRANSPARENCY:
 		//case FEATURE_HIDPI:
 		case FEATURE_ICON:
-		case FEATURE_NATIVE_ICON:
+		//case FEATURE_NATIVE_ICON:
 		case FEATURE_SWAP_BUFFERS:
 #ifdef DBUS_ENABLED
 		case FEATURE_KEEP_SCREEN_ON: