Update Configuration-Settings.md

1) Update config documentation changed in this [PR](https://github.com/mattermost/platform/pull/1555/files#diff-6a02156604c06becbe5fdca178766accL71)

doc/install/Configuration-Settings.md

@@ -291,16 +291,13 @@ System Console allows an IT Admin to update settings defined in `config.json`. H
 ```"EnableOAuthServiceProvider": false```  
 ”true”: Allow Mattermost to function as an OAuth provider, allowing 3rd party apps access to your user store for authentication.
 
-### Push Notification Settings
+### Email Settings
 
-```"ApplePushServer": ""```  
+```"SendPushNotifications": true```  
-Setting for features in development.
+"true": Your mattermsot server sends mobile push notifications to the server specified in **PushNotificationServer**; "false": Mobile push notifications are disabled.
 
-```"ApplePushCertPublic": ""```  
+```"PushNotificationServer": "https://push.mattermost.com"```  
-Setting for features in development.
+Address of the proxy server that re-sends push notifications to their respective services like APNS (Apple Push Notification Services).
-
-```"ApplePushCertPrivate": ""```  
-Setting for features in development.
 
 ### File Settings