Revert .env.example to 2.4 branch default

.env.example

@@ -1,10 +1,13 @@
 APP_ENV=production
 APP_DEBUG=false
 APP_URL=http://localhost
-APP_KEY=SomeRandomString
+APP_TIMEZONE=UTC
+APP_KEY=
+DEBUGBAR_ENABLED=false
 
 DB_DRIVER=mysql
 DB_HOST=localhost
+DB_UNIX_SOCKET=null
 DB_DATABASE=cachet
 DB_USERNAME=homestead
 DB_PASSWORD=secret
@@ -14,11 +17,14 @@ DB_PREFIX=null
 CACHE_DRIVER=file
 SESSION_DRIVER=file
 QUEUE_DRIVER=sync
-CACHET_EMOJI=false
 
-MAIL_DRIVER=smtp
-MAIL_HOST=mailtrap.io
-MAIL_PORT=2525
+CACHET_BEACON=true
+CACHET_EMOJI=false
+CACHET_AUTO_TWITTER=true
+
+MAIL_DRIVER=log
+MAIL_HOST=null
+MAIL_PORT=null
 MAIL_USERNAME=null
 MAIL_PASSWORD=null
 MAIL_ADDRESS=null
@@ -30,3 +36,9 @@ REDIS_DATABASE=null
 REDIS_PORT=null
 
 GITHUB_TOKEN=null
+
+NEXMO_KEY=null
+NEXMO_SECRET=null
+NEXMO_SMS_FROM=Cachet
+
+TRUSTED_PROXIES=