main.yml in belated-0.8.0

- old
+ new

@@ -5,12 +5,12 @@
 jobs:
   build:
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu-latest, macos-latest]
+        os: [ubuntu-latest]
         # Due to https://github.com/actions/runner/issues/849, we have to use quotes for '3.0'
-        ruby: [2.7, '3.0']
+        ruby: [2.6, 2.7, '3.0']
     runs-on: ${{ matrix.os }}
     steps:
     - uses: actions/checkout@v2
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1