refactor: make nickname field optional in chat user serializer

Author: wxg0103

apps/system_manage/serializers/chat_user.py

@@ -288,7 +288,7 @@ class UserEditInstance(serializers.Serializer):
             allow_blank=True,
         )
         nick_name = serializers.CharField(
-            required=True,
+            required=False,
             label=_("Name"),
             max_length=64,
         )