fix: limit characters and lines so redact message can't be too long

Before, if the user typed too many lines it would overflow past the input box and also leave a very long message in chat. Now, it is limited and won't expand in the input box past 4 lines.

lib/pages/chat/chat.dart

@@ -843,6 +843,9 @@ class ChatController extends State<ChatPageWithRoom>
             message: L10n.of(context).redactMessageDescription,
             isDestructive: true,
             hintText: L10n.of(context).optionalRedactReason,
+            maxLength: 255,
+            maxLines: 3,
+            minLines: 1,
             okLabel: L10n.of(context).remove,
             cancelLabel: L10n.of(context).cancel,
           )