ci: reintroduce pypy in tested python versions

In an attempt to fix #60

Author: mthh

.github/workflows/ci-tests.yml

@@ -26,8 +26,9 @@ jobs:
             '3.10',
             '3.11',
             '3.12',
-            '3.13'
-            # pypy3  # didn't build on CI anymore, happy for help: https://github.com/mthh/routingpy/issues/60
+            '3.13',
+            'pypy3.9',
+            'pypy3.10',
         ]
     steps:
     - uses: actions/checkout@v4