Fix GitHub Codespaces link in README

Updated GitHub Codespaces link to point to the correct tutorial repository.

Author: jackdmarquez

hands-on/session III/README.md

@@ -59,7 +59,7 @@ Use your GitHub account to run this tutorial with GitHub Codespaces
 
 Please click the next button to open in GitHub Codespaces
 
-[![Open in GitHub Codespaces](https://github.com/codespaces/badge.svg)](https://github.com/codespaces/new/TauferLab/NSDF-Tutorial-2025?devcontainer_path=.devcontainer/session+III/devcontainer.json)
+[![Open in GitHub Codespaces](https://github.com/codespaces/badge.svg)](https://github.com/codespaces/new/TauferLab/NSDF-tutorial?devcontainer_path=.devcontainer/session+II/devcontainer.json)
 
 Now follow these steps to set up your virtual environment using GitHub codespaces: