fix

Author: hiraokashi

.github/workflows/ci.yml

@@ -12,7 +12,7 @@ jobs:
         # TODO: Wait for supporting Ruby 3.0 in simplecov-cobertura.
         # See https://github.com/dashingrocket/simplecov-cobertura/pull/16
         # ruby: [ 2.5, 2.6, 2.7, 3.0 ]
-        ruby: [ 3.0, 3.1, 3.2 ,3.3]
+        ruby: [ '3.0', '3.1', '3.2', '3.3' ]
         exclude:
          - { os: macos-latest, ruby: '2.5' }
     runs-on: ${{ matrix.os }}