api [nfc]: Remove comment about deprecated away in user status

Fixes-partly: #1837

Author: chrisbobbe

lib/api/model/model.dart

@@ -257,7 +257,6 @@ class StatusEmoji {
 ///
 /// The absence of one of these means there is no change.
 class UserStatusChange {
-  // final Option<bool> away; // deprecated in server-6 (FL-148); ignore
   final Option<String?> text;
   final Option<StatusEmoji?> emoji;