ci.yaml in openapi_parser-1.0.0

- old
+ new

@@ -4,10 +4,10 @@
   test:
     strategy:
       fail-fast: false
       matrix:
         os: [ubuntu-latest, macos-latest]
-        ruby: [2.6, 2.7, '3.0', head]
+        ruby: [2.6, 2.7, '3.0', '3.1']
     runs-on: ${{ matrix.os }}
     steps:
     - uses: actions/checkout@v2
     - uses: ruby/setup-ruby@v1
       with: