update ruby

Author: JASON13F

.github/workflows/pr_check.yml

@@ -26,7 +26,7 @@ jobs:
 
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: 2.7.2
+          ruby-version: 3.1
           bundler-cache: true
       - name: Run danger
         env: