Proposed changelog update regarding AppConfig compatability (#2688)

Make it more obvious what action needs to be taken + some readability updates

CHANGELOG.md

@@ -6,7 +6,7 @@
 
 ### Combatibility
  - If **DisableLegacyMfa** setting in ``config.json`` is set to ``true`` and [multi-factor authentication](https://docs.mattermost.com/deployment/auth.html) is enabled, ensure your users have upgraded to mobile app version 1.17 or later. See [Important Upgrade Notes](https://docs.mattermost.com/administration/important-upgrade-notes.html) for more details.
- - Fixed support for EMM connections using VPN on-demand to indicate that every request should wait for the VPN connection to be establish and to set the value in seconds for the timeout. See docs for more details on [setting AppConfig values](https://docs.mattermost.com/mobile/mobile-appconfig.html#mattermost-appconfig-values) for VPN support.
+ - If you are using an EMM provider via AppConfig, make sure to add two new settings, `useVPN` and `timeoutVPN`, to your AppConfig file. The settings were added for EMM connections using VPN on-demand - one to indicate if every request should wait for the VPN connection to be established, and another to set the timeout in seconds. See docs for more details on [setting AppConfig values](https://docs.mattermost.com/mobile/mobile-appconfig.html#mattermost-appconfig-values) for VPN support.
  - Mobile App v1.13+ is required for Mattermost Server v5.4+.
  - Android operating system 7+ [is required by Google](https://android-developers.googleblog.com/2017/12/improving-app-security-and-performance.html).
  - iPhone 5s devices and later with iOS 11+ is required.