Update docs, remove App.net since service is shutting down
* vertx-auth provides you with many out of the box implementations:
*
*
- * * App.net {@link io.vertx.ext.auth.oauth2.providers.AppNetAuth}
* * Azure Active Directory {@link io.vertx.ext.auth.oauth2.providers.AzureADAuth}
* * Box.com {@link io.vertx.ext.auth.oauth2.providers.BoxAuth}
* * Dropbox {@link io.vertx.ext.auth.oauth2.providers.DropboxAuth}
