actions: run coverage on python 3.14

Author: ebonnal

.github/workflows/coverage.yml

@@ -13,10 +13,10 @@ jobs:
 
     steps:
       - uses: actions/checkout@v4
-      - name: Set up Python 3.9
-        uses: actions/setup-python@v1
+      - name: Set up Python 3.14
+        uses: actions/setup-python@v4
         with:
-          python-version: 3.9
+          python-version: '3.14.0-alpha.3'
 
       - name: unittest
         run: |