📝 Update release notes

[skip ci]

docs/en/docs/release-notes.md

@@ -15,6 +15,7 @@ hide:
 
 ### Fixes
 
+* ⚡️ Fix `default_factory` for response model field with Pydantic V1. PR [#9704](https://github.com/fastapi/fastapi/pull/9704) by [@vvanglro](https://github.com/vvanglro).
 * 🐛 Fix inconsistent processing of model docstring formfeed char with Pydantic V1. PR [#6039](https://github.com/fastapi/fastapi/pull/6039) by [@MaxwellPayne](https://github.com/MaxwellPayne).
 * 🐛 Fix `jsonable_encoder` alters `json_encoders` of Pydantic v1 objects. PR [#4972](https://github.com/fastapi/fastapi/pull/4972) by [@aboubacs](https://github.com/aboubacs).
 * 🐛 Reenable `allow_arbitrary_types` when only 1 argument is used on the API endpoint. PR [#13694](https://github.com/fastapi/fastapi/pull/13694) by [@rmawatson](https://github.com/rmawatson).