Use latest stable Ruby and Node Docker images

Ruby 4.0 and Node 24 (LTS) are the current stable releases.

Author: bbatsov

.circleci/config.yml

@@ -3,7 +3,7 @@ version: 2
 jobs:
   docs-build:
     docker:
-      - image: ruby:3.3
+      - image: ruby:4.0
     steps:
       - checkout
       - run:
@@ -19,7 +19,7 @@ jobs:
           paths: html
   docs-deploy:
     docker:
-      - image: node:20
+      - image: node:24
     steps:
       - checkout
       - attach_workspace: