ci: remove Python 3.13 from test matrix, keep only 3.12

Author: jeremyeder

.github/workflows/tests.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ['3.12', '3.13']
+        python-version: ['3.12']
 
     steps:
       - name: Checkout code