Update plugin.json (mattermost#631)

Author: nydhy

plugin.json

@@ -27,7 +27,7 @@
                 "key": "UsePreregisteredApplication",
                 "display_name": "Use Preregistered OAuth Application:",
                 "type": "bool",
-                "help_text": "When true, instructs the plugin to use the preregistered GitHub OAuth application - application registration steps can be skipped. Requires [Chimera Proxy](https://github.com/mattermost/chimera) URL to be configured for the server. Cannot be used with GitHub enterprise. **This setting is intended to be used with Mattermost Cloud instances only.**",
+                "help_text": "Set to false if using GitHub Enterprise. When true, instructs the plugin to use the preregistered GitHub OAuth application - application registration steps can be skipped. Requires [Chimera Proxy](https://github.com/mattermost/chimera) URL to be configured for the server. Cannot be used with GitHub enterprise. **This setting is intended to be used with Mattermost Cloud instances only.**",
                 "default": false
             },
             {