test: bump pypy to latest available

We need pypy 7.3.10+ anyway to perform the SSL test because cryptography is not available before.

Author: StephenSorriaux

.github/workflows/testing.yml

@@ -52,7 +52,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        python-version: ["3.7", "3.8", "3.9", "3.10", "pypy-3.7"]
+        python-version: ["3.7", "3.8", "3.9", "3.10", "pypy-3.10-v7.3.15"]
         zk-version: ["3.4.14", "3.5.10", "3.6.3", "3.7.1"]
         include:
           - python-version: "3.7"
@@ -63,7 +63,7 @@ jobs:
             tox-env: py39
           - python-version: "3.10"
             tox-env: py310
-          - python-version: "pypy-3.7"
+          - python-version: "pypy-3.10-v7.3.15"
             tox-env: pypy3
     steps:
       - uses: actions/checkout@v4