Help renovate find the version it needs to update for ruby

Dockerfile

 # syntax = docker/dockerfile:1
 
 # Make sure RUBY_VERSION matches the Ruby version in .ruby-version and Gemfile
+# renovate: datasource=docker depName=registry.docker.com/library/ruby
 ARG RUBY_VERSION=3.3.6
 FROM registry.docker.com/library/ruby:$RUBY_VERSION-slim AS base
 

renovate.json

@@ -16,7 +16,7 @@
         "mcr.microsoft.com/devcontainers/ruby",
         "registry.docker.com/library/ruby"
       ],
-      "groupName": "ruby-updates"
+      "groupName": "ruby"
     }
   ]
 }