Fix CI (#1242)

* ci.yml: Disable "fail fast"

.. to better see if failure depends on architecture and/or Python
version only

* ci.yml: Stop CI from trying Python 3.7 on arm64 macOS

Symptom was this error:
> Error: The version '3.7' with architecture 'arm64' was not found for macOS 14.6.1.
> The list of all available versions can be found here: https://raw.githubusercontent.com/actions/python-versions/main/versions-manifest.json

Note that Python 3.7 is end-of life since 2023-06-27.

.github/workflows/ci.yml

@@ -11,8 +11,9 @@ jobs:
   build:
     runs-on: ${{ matrix.os }}
     strategy:
+      fail-fast: false
       matrix:
-        python-version: ["3.7", "3.11", "3.12"]  # no particular need for 3.9 or 3.10
+        python-version: ["3.8", "3.11", "3.12"]  # no particular need for 3.9 or 3.10
         os: [macos-latest, ubuntu-latest, windows-latest]
     steps:
     - uses: actions/checkout@9bb56186c3b09b4f86b1c65136769dd318469633  # v4.1.2