CI: test with pypy-3.9

Author: sebastinas

.github/workflows/build.yaml

@@ -20,7 +20,7 @@ jobs:
         - "3.11"
         - "3.12"
         - "3.13"
-        - "pypy-3.8"
+        - "pypy-3.9"
     steps:
     - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python-version }}