revert env var

packages/app/.env.development

@@ -5,7 +5,7 @@
 FILE_UPLOAD=mongodb
 # MONGO_GRIDFS_TOTAL_LIMIT=10485760
 MATHJAX=1
-NO_CDN=true
+# NO_CDN=true
 MONGO_URI="mongodb://mongo:27017/growi"
 # REDIS_URI="http://redis:6379"
 # NCHAN_URI="http://nchan"