Update Python version in TestPyPI workflow to 3.12

- Changed the Python version from 3.9 to 3.12 in the GitHub Actions workflow for publishing to TestPyPI, ensuring compatibility with the latest features and improvements.

Author: JoshuaHarris391

.github/workflows/publish_testpypi.yml

@@ -14,7 +14,7 @@ jobs:
       - name: Set up Python
         uses: actions/setup-python@v4
         with:
-          python-version: 3.9
+          python-version: 3.12
 
       - name: Install Poetry
         run: |