Shortened warning audio by 50%, updated file name to mp3.

Author: Miguel

ini-atc-desktop/assets/sounds/warning.mp3

@@ -71,7 +71,7 @@ public static void load() {
 
 	private static void loadSounds() {
 		sounds.put("ding", loadSound("ding.wav"));
-		sounds.put("warning", loadSound("warning.wav"));
+		sounds.put("warning", loadSound("warning.mp3"));
 		sounds.put("crash", loadSound("crash.mp3"));
 		sounds.put("national", loadSound("national.mp3"));
 		sounds.put("ambience", loadSound("ambience.mp3"));