fix installer for github actions

Author: hjwp

.github/workflows/tests.yml

@@ -65,9 +65,9 @@ jobs:
           git config --global init.defaultBranch main
 
       - name: Set up Python 3.14
-        uses: actions/setup-python@v5
+        uses: actions/setup-python@v6
         with:
-          python-version: '3.14'
+          python-version: '3.14.0-rc.3'
 
       - name: Install apt stuff and other dependencies
         shell: bash