📝 Update source examples and docs from Python 3.9 to 3.10 (#14900)

docs_src/encoder/tutorial001_py39.py

@@ -1,23 +0,0 @@
-from datetime import datetime
-from typing import Union
-
-from fastapi import FastAPI
-from fastapi.encoders import jsonable_encoder
-from pydantic import BaseModel
-
-fake_db = {}
-
-
-class Item(BaseModel):
-    title: str
-    timestamp: datetime
-    description: Union[str, None] = None
-
-
-app = FastAPI()
-
-
-@app.put("/items/{id}")
-def update_item(id: str, item: Item):
-    json_compatible_item_data = jsonable_encoder(item)
-    fake_db[id] = json_compatible_item_data