CI: Add allow-prereleases: true

.github/workflows/ci_np2.yml

@@ -17,6 +17,7 @@ jobs:
       uses: actions/setup-python@v3
       with:
         python-version: '3.13'
+        allow-prereleases: true
     - name: Add conda to system path
       run: |
         # $CONDA is an environment variable pointing to the root of the miniconda directory