Typing error

### Apache Airflow version 3.0.3 ### If "Other Airflow 2 version" selected, which one? 3.0.2 ### What happened? I wrote a custom deferrable Operator, that uses a custom trigger for deferring. The custom trigger should fail/succeed the task (yielding `TaskFailedEvent` or `TaskSuccessEvent`). According to the [docstrings](https://github.com/apache/airflow/blob/8fb611667e83ac037ee16722549efedef7350ee7/task-sdk/src/airflow/sdk/bases/operator.py#L1586), I should pass `method_name=None` in this case. However, that leads to a typing issue because `method_name` has type `string `rather than `Optional(string)` Indeed, the task fails with a validation error: ``` - Top level error: source="task" ValidationError: 1 validation error for DeferTask next_method Input should be a valid string [type=string_type, input_value=None, input_type=NoneType] ``` ### What you think should happen instead? When passing `None` as `next_method`, the task should be failed/succeeded directly from the trigger. ### How to reproduce Define a custom deferrable Operator, that uses a custom trigger for deferring. The custom trigger should only fail/succeed the task (yielding TaskFailedEvent or TaskSuccessEvent). Define the custom operator's `execute` function as : ``` def execute(self): self.defer( trigger=CustomTrigger(), method_name=None, # type:ignore # according to docs: # If the trigger will end the task instance itself, # ``method_name`` should be None # But it's not nullable ) ``` And use the custom operator as a single task in a dag ### Operating System RedHat Openshift ### Versions of Apache Airflow Providers _No response_ ### Deployment Official Apache Airflow Helm Chart ### Deployment details _No response_ ### Anything else? _No response_ ### Are you willing to submit PR? - [ ] Yes I am willing to submit a PR! ### Code of Conduct - [x] I agree to follow this project's [Code of Conduct](https://gi…