Examples: Avoid mipmaps in exr envmap demo.

examples/webgl_materials_envmaps_exr.html

@@ -100,11 +100,7 @@
 
 					texture.encoding = THREE.sRGBEncoding;
 
-					var options = {
-						generateMipmaps: true
-					};
-
-					pngBackground = new THREE.WebGLRenderTargetCube( 512, 512, options ).fromEquirectangularTexture( renderer, texture );
+					pngBackground = new THREE.WebGLRenderTargetCube( 512, 512 ).fromEquirectangularTexture( renderer, texture );
 
 					var pmremGenerator = new PMREMGenerator( pngBackground.texture );
 					pmremGenerator.update( renderer );