📝 Update release notes

[skip ci]

Author: github-actions

docs/release-notes.md

@@ -6,6 +6,10 @@
 
 * 🚚 Rename test to corner-cases to make it more explicit. PR [#1083](https://github.com/fastapi/typer/pull/1083) by [@tiangolo](https://github.com/tiangolo).
 
+### Docs
+
+* 📝 Clarify the need for `mix_stderr` when accessing the output of `stderr` in tests. PR [#1045](https://github.com/fastapi/typer/pull/1045) by [@mrchrisadams](https://github.com/mrchrisadams).
+
 ### Internal
 
 * ⬆ Bump ruff from 0.9.6 to 0.9.7. PR [#1161](https://github.com/fastapi/typer/pull/1161) by [@dependabot[bot]](https://github.com/apps/dependabot).