CI: Drop testing on Python 3.7 (#61)

Python 3.7 is reaching its end-of-life status.

Author: ghisvail

.github/workflows/test.yaml

@@ -32,7 +32,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest]
-        python-version: ['3.7', '3.8', '3.9', '3.10', '3.11']
+        python-version: ['3.8', '3.9', '3.10', '3.11']
     runs-on: ${{ matrix.os }}
     steps:
       - uses: actions/checkout@v3