GLTFLoader: Remove 'experimental' status on lights.

docs/examples/loaders/GLTFLoader.html

@@ -31,7 +31,7 @@
 			<li>KHR_draco_mesh_compression</li>
 			<li>KHR_materials_pbrSpecularGlossiness</li>
 			<li>KHR_materials_unlit</li>
-			<li>KHR_lights_punctual (experimental)</li>
+			<li>KHR_lights_punctual</li>
 			<li>KHR_texture_transform<sup>*</sup></li>
 			<li>MSFT_texture_dds</li>
 		</ul>