Recommend developing with Python 3.12 in developer guide (#15811)

Signed-off-by: Harry Mellor <19981378+hmellor@users.noreply.github.com>
Co-authored-by: Cyrus Leung <cyrus.tl.leung@gmail.com>

docs/source/contributing/overview.md

@@ -44,6 +44,12 @@ pre-commit run --all-files
 pytest tests/
 ```
 
+:::{tip}
+Since the <gh-file:Dockerfile> ships with Python 3.12, all tests in CI (except `mypy`) are run with Python 3.12.
+
+Therefore, we recommend developing with Python 3.12 to minimise the chance of your local environment clashing with our CI environment.
+:::
+
 :::{note}
 Currently, the repository is not fully checked by `mypy`.
 :::