Fix CameraHelper docs typo

docs/api/extras/helpers/CameraHelper.html

@@ -24,8 +24,7 @@
 
 		<code>
 var camera = new THREE.PerspectiveCamera( 75, window.innerWidth / window.innerHeight, 0.1, 1000 );
-
-var helper = new THREE.CameraHelper( cameraPerspective );
+var helper = new THREE.CameraHelper( camera );
 scene.add( helper );
 		</code>