Adding comment about using 2.25 as root for UUID based UID

[JJdeRidder]

Description

Added a comment about using 2.25 as root in generate_uid instead of PYMEDPHYS it's root.

(I hope im doing this right, this is my first time contributing something to a project)

Related issues: #130

Checklist

• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] My changes generate no new warnings
• [ ] My code follows the style guidelines of this project

Open questions

Should I change the value of ORG_ROOT to 2.25?

[vsoch]

Oh and to answer your question, I think since it's a dummy example / docs, we can leave that change up to the user depending on his/her use case.