ci: drop python 3.7 on mac

github actions runners do not include this image:

Version 3.7 was not found in the local cache
Error: The version '3.7' with architecture 'arm64' was not found for macOS 14.4.1.
The list of all available versions can be found here: https://raw.githubusercontent.com/actions/python-versions/main/versions-manifest.json

.github/workflows/ci.yml

@@ -22,6 +22,10 @@ jobs:
       matrix:
         python-version: [3.7, 3.8, 3.9, '3.10', 3.11]
         os: [ubuntu-latest, macos-latest, windows-latest]
+        exclude:
+          # 3.7 is dropped on macos 14 runners
+          - python-version: '3.7'
+            os: macos
 
     steps:
     - name: Checkout sources