Bone: Removed redundant copy().

src/objects/Bone.js

@@ -18,15 +18,7 @@ Bone.prototype = Object.assign( Object.create( Object3D.prototype ), {
 
 	constructor: Bone,
 
-	isBone: true,
-
-	copy: function ( source ) {
-
-		Object3D.prototype.copy.call( this, source );
-
-		return this;
-
-	}
+	isBone: true
 
 } );