Upgrade Python in docker

Following the instructions here:
Set up Development Environment | Home Assistant Developer Docs (home-assistant.io)

I installed docker and started developing on windows. Everything sounds ok…
… but I get every time this error:
Support for Python 3.9.15 is being removed
This stops working in version 2023.2. Please address before upgrading.

How can I upgrade?
I even tried to rebase my fork on the current one but python did not get updated