dag parse stdout goes to warning on celery worker

### Body

not sure why but here's an example

sample code

```
from time import sleep

from airflow import DAG
from airflow.decorators import task
from airflow.models.baseoperator import chain_linear

with DAG(dag_id="dag1", catchup=False):

@task
def the_task():
sleep(10)

tasks = []
for num in range(3):
tasks.append(the_task.override(task_id=f"task_{num+1}")())

chain_linear(*tasks)

print("HI I AM HERE")
```

celery worker output

this can pollute worker logs if you have a really chatty dag

### Committer

- [X] I acknowledge that I am a maintainer/committer of the Apache Airflow project.

No file or test is named. Start by reproducing the sample DAG with a Celery worker and trace how stdout from DAG parsing is classified; done means ordinary DAG stdout no longer appears as a warning or pollutes worker logs.

Written by the indexing model from the issue text.