Use Python 3.12 in CI testing matrix

Update the GitHub Actions testing matrix to run on Python 3.12 instead of 3.11. This moves CI to test against the newer Python runtime while keeping existing matrix include entries unchanged.

Author: C-Achard

.github/workflows/testing-ci.yml

@@ -85,7 +85,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python: ['3.11']
+        python: ['3.12']
         include:
           - label: pypi-1.1
             dlclive_spec: deeplabcut-live==1.1