🔥 Remove Python 3.9 specific files, no longer needed after updating translations (#14931)

docs_src/background_tasks/tutorial001_py39.py

@@ -1,15 +0,0 @@
-from fastapi import BackgroundTasks, FastAPI
-
-app = FastAPI()
-
-
-def write_notification(email: str, message=""):
-    with open("log.txt", mode="w") as email_file:
-        content = f"notification for {email}: {message}"
-        email_file.write(content)
-
-
-@app.post("/send-notification/{email}")
-async def send_notification(email: str, background_tasks: BackgroundTasks):
-    background_tasks.add_task(write_notification, email, message="some notification")
-    return {"message": "Notification sent in the background"}