Update tutorial002.py

Replace deprecated `@app.on_event("startup")` with lifecycle event approach.

docs_src/sql_databases/tutorial002.py

@@ -1,4 +1,5 @@
 from typing import List, Union
+from contextlib import asynccontextmanager
 
 from fastapi import Depends, FastAPI, HTTPException, Query
 from sqlmodel import Field, Session, SQLModel, create_engine, select
@@ -43,14 +44,13 @@ def get_session():
     with Session(engine) as session:
         yield session
 
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    models.create_db_and_tables()
+    yield
+    # Can add events for after startup completion here
 
-app = FastAPI()
-
-
-@app.on_event("startup")
-def on_startup():
-    create_db_and_tables()
-
+app = FastAPI(lifespan=lifespan)
 
 @app.post("/heroes/", response_model=HeroPublic)
 def create_hero(hero: HeroCreate, session: Session = Depends(get_session)):