Use release version of Python 3.12 for doctest

Author: hugovk

.github/workflows/reusable-docs.yml

@@ -113,7 +113,7 @@ jobs:
 #    - name: 'Build CPython'
 #      run: make -j4
     - name: 'Install build dependencies'
-      run: make -C Doc/ PYTHON=../python venv
+      run: make -C Doc/ PYTHON=python3 venv
     # Use "xvfb-run" since some doctest tests open GUI windows
     - name: 'Run documentation doctest'
       run: xvfb-run make -C Doc/ PYTHON=../python SPHINXERRORHANDLING="-W --keep-going" doctest