Remove old and completed TODO

Author: Zorbatron

src/main/java/gregtech/api/items/metaitem/stats/IMouseEventHandler.java

@@ -18,7 +18,6 @@
 
 import java.util.function.Consumer;
 
-// TODO: add EnumHand to the methods/support for offhand items
 /**
  * Implement on your {@link IItemComponent} to handle mouse events while the corresponding item is selected on the main
  * hotbar. <br/>