GHA CI: Add python 3.15 to test matrix

Author: xavier2k6

.github/workflows/ci.yaml

@@ -15,7 +15,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ['3.9', '3.10', '3.11', '3.12', '3.13', '3.14-dev']
+        python-version: ['3.9', '3.10', '3.11', '3.12', '3.13', '3.14', '3.15-dev']
     defaults:
       run:
         working-directory: nova3