webgl_materials_envmaps: Remove unused variable

The variable `timer` is written, but never read.

examples/webgl_materials_envmaps.html

@@ -211,8 +211,6 @@
 
 			function render() {
 
-				var timer = -0.0002 * Date.now();
-
 				camera.lookAt( scene.position );
 				cameraCube.rotation.copy( camera.rotation );