Revert "bypass self.__WB_MANIFEST check"

This reverts commit afd8acd69d.

sw/index.js

@@ -5,8 +5,8 @@ import { NetworkOnly } from 'workbox-strategies'
 import manifest from './precache-manifest.json'
 
 // ignore precache manifest generated by InjectManifest
-// they statically check for the presence of this variable
-console.log(self.__WB_MANIFEST)
+// self.__WB_MANIFEST
+
 precacheAndRoute(manifest)
 
 self.addEventListener('install', () => {