ubuntu.yml in yao-0.14.0

- old
+ new

@@ -5,10 +5,10 @@
 jobs:
   build:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        ruby: [ '2.6.x', '2.5.x', '2.4.x' ]
+        ruby: [3.0, 2.7, 2.6]
     steps:
     - uses: actions/checkout@master
     - name: Set up Ruby
       uses: actions/setup-ruby@v1
       with: