Migrate set-output to $GITHUB_OUTPUT ruby#17

https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

Author: b-sakata

.github/workflows/test.yml

@@ -15,7 +15,7 @@ jobs:
       - id: versions
         run: |
           versions=$(curl -s 'https://cache.ruby-lang.org/pub/misc/ci_versions/cruby.json' | jq -c '. + ["jruby", "truffleruby-head"]')
-          echo "::set-output name=value::${versions}"
+          echo "value=${versions}" >> $GITHUB_OUTPUT
   test:
     needs: ruby-versions
     name: build (${{ matrix.ruby }} / ${{ matrix.os }})