improve env.dev.js for debug

config/env.dev.js

@@ -1,6 +1,6 @@
 module.exports = {
   NODE_ENV: 'development',
-  MATHJAX: 1,
+  // MATHJAX: 1,
   // REDIS_URL: 'redis://localhost:6379/crowi',
   // ELASTICSEARCH_URI: 'http://localhost:9200/crowi',
   PLUGIN_NAMES_TOBE_LOADED: [