Downgrade macos runner

See actions/setup-python#825

Author: daneah

.github/workflows/ci.yaml

@@ -14,7 +14,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        os: [ubuntu-latest, macos-latest, windows-latest]
+        os: [ubuntu-latest, macos-13, windows-latest]
         python-version: ["3.7", "3.8", "3.9", "3.10", "3.11"]
     defaults:
       run: