Configure Ruby version and bundler cache for Danger workflow.

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Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: dblock

.github/workflows/danger.yml

@@ -8,3 +8,6 @@ jobs:
   danger:
     uses: numbata/danger-pr-comment/.github/workflows/danger-run.yml@main
     secrets: inherit
+    with:
+      ruby-version: '3.1'
+      bundler-cache: true