Apply dedent when docstring is passed as task doc

### Description

When using task decorator, task documentation can be passed using via the function docstring like this

```python
@task(task_display_name="My task")
def my_task(**context):
"""
This task do ...

In case of error you should do ...
"""
```

Unfortuntally, since no dedent is applied the display in the user interface is unattractive. It's possible to achieve a good result by removing the indentation from the DAG file, but this makes the code less readable.

### Use case/motivation

_No response_

### Related issues

_No response_

### Are you willing to submit a PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [x] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)