fix github actions for 3.7

Author: mahmoud

.github/workflows/tests.yaml

@@ -25,7 +25,7 @@ jobs:
           - { name: "3.10", python: "3.10", os: ubuntu-latest, tox: py310 }
           - { name: "3.9", python: "3.9", os: ubuntu-latest, tox: py39 }
           - { name: "3.8", python: "3.8", os: ubuntu-latest, tox: py38 }
-          - { name: "3.7", python: "3.7", os: ubuntu-latest, tox: py37 }
+          - { name: "3.7", python: "3.7", os: ubuntu-22.04, tox: py37 }
           - { name: "PyPy3", python: "pypy-3.9", os: ubuntu-latest, tox: pypy3 }
     steps:
       - uses: actions/checkout@v4