Doc: Sync Matrix4.html with En doc.

docs/api/zh/math/Matrix4.html

@@ -51,7 +51,7 @@
 
 				这意味着
 		<code>
-var m = new Matrix4();
+var m = new THREE.Matrix4();
 
 m.set( 11, 12, 13, 14,
        21, 22, 23, 24,