Run less macOS and Windows CI jobs

They are very subject to timeouts and such.
By testing only the oldest and newest versions on them
we might have less flakiness.

Author: byroot

.github/workflows/ci.yaml

@@ -14,8 +14,17 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu, macos, windows]
+        os: [ubuntu]
         ruby: ['2.5', '2.6', '2.7', '3.0', '3.1', '3.2']
+        include:
+          - os: macos
+            ruby: '2.5'
+          - os: macos
+            ruby: '3.2'
+          - os: windows
+            ruby: '2.5'
+          - os: windows
+            ruby: '3.2'
     runs-on: ${{ matrix.os }}-latest
     steps:
       - uses: actions/checkout@v2
@@ -31,7 +40,7 @@ jobs:
       - uses: actions/checkout@v2
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: 3.1
+          ruby-version: '3.1'
           bundler-cache: true # 'bundle install' and cache
       - run: sudo apt-get install -y valgrind
       - run: bundle exec rake spec:valgrind