fix: pin ruby/setup-ruby action to full commit SHA

GitHub org policy requires all actions to be pinned to full-length
commit SHAs. Pin ruby/setup-ruby@v1 to its current SHA.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: mikolalysenko

.github/workflows/ci.yml

@@ -143,7 +143,7 @@ jobs:
 
       - name: Setup Ruby
         if: matrix.suite == 'e2e_gem'
-        uses: ruby/setup-ruby@v1
+        uses: ruby/setup-ruby@319994f95fa847cf3fb3cd3dbe89f6dcde9f178f # v1
         with:
           ruby-version: '3.2'
           bundler-cache: false