Bump Ruby version to 3.2 on CI

Author: KitaitiMakoto

.github/workflows/bindings-ruby.yml

@@ -16,6 +16,6 @@ jobs:
     steps:
       - uses: ruby/setup-ruby@v1
         with:
-          ruby-version: '3.1'
+          ruby-version: '3.2'
       - uses: actions/checkout@v4
       - run: rake test