LightProbeFactory: correct a typographic error in the javadoc

jme3-core/src/main/java/com/jme3/environment/LightProbeFactory.java

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2009-2019 jMonkeyEngine
+ * Copyright (c) 2009-2020 jMonkeyEngine
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -208,7 +208,7 @@ public class LightProbeFactory {
     }
 
     /**
-     * For debuging porpose only
+     * For debuging purposes only.
      * Will return a Node meant to be added to a GUI presenting the 2 cube maps in a cross pattern with all the mip maps.
      *
      * @param manager the asset manager