Specify python version for pre (#2276)

Author: minrk

.github/workflows/tests.yml

@@ -168,6 +168,7 @@ jobs:
       - uses: jupyterlab/maintainer-tools/.github/actions/base-setup@v1
         with:
           dependency_type: pre
+          python_version: "3.14"
       - name: Run the tests
         run: |
           export NBFORMAT_VALIDATOR=jsonschema