📝 Update release notes

docs/release-notes.md

@@ -1,5 +1,6 @@
 ## Latest changes
 
+* Generate correct OpenAPI docs for responses with no content. PR [#621](https://github.com/tiangolo/fastapi/pull/621) by [@brotskydotcom](https://github.com/brotskydotcom).
 * Remove `$` from Bash code blocks in docs for consistency. PR [#613](https://github.com/tiangolo/fastapi/pull/613) by [@nstapelbroek](https://github.com/nstapelbroek).
 * Add docs for [self-serving docs' (Swagger UI) static assets](https://fastapi.tiangolo.com/tutorial/extending-openapi/#self-hosting-javascript-and-css-for-docs), e.g. to use the docs offline, or without Internet. Initial PR [#557](https://github.com/tiangolo/fastapi/pull/557) by [@svalouch](https://github.com/svalouch).
 * Fix `black` linting after upgrade. PR [#682](https://github.com/tiangolo/fastapi/pull/682) by [@frankie567](https://github.com/frankie567).