Fix macos versions and pip caching

Author: cjrh

.github/workflows/pythonapp.yml

@@ -9,11 +9,11 @@ jobs:
     timeout-minutes: 5
     strategy:
       matrix:
-        python-version: ['3.6', '3.7', '3.8', '3.9', '3.10', '3.11', '3.12', '3.13', 'pypy3.10']
+        python-version: ['3.8', '3.9', '3.10', '3.11', '3.12', '3.13', 'pypy3.10']
         os: [ubuntu-latest, windows-latest, macOS-latest]
         exclude:
           - os: macOS-latest
-            python-version: '3.6'
+            python-version: ['3.8', '3.9', '3.10']
           - os: macOS-latest
             python-version: 'pypy3'
       fail-fast: false
@@ -23,6 +23,7 @@ jobs:
       uses: actions/setup-python@v5
       with:
         python-version: ${{ matrix.python-version }}
+        cache: 'pip'
         architecture: x64
     - name: Install dependencies
       run: |