Update ruby/setup-ruby digest to 6615b4b (#13962)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

.github/workflows/pre-release.yml

@@ -68,7 +68,7 @@ jobs:
           fetch-tags: true
           ref: release-${{ github.event.inputs.version }}
       - name: Install Ruby
-        uses: ruby/setup-ruby@5f19ec79cedfadb78ab837f95b87734d0003c899
+        uses: ruby/setup-ruby@6615b4b8a02c78c4d711c06df4b8a20aa685a45d
         with:
           ruby-version: '3.1'
           working-directory: 'rb'