docs(ruby-runtime): clarify core_ext.rb comment about backward compatibility

Author: omarqureshi

packages/@jsii/ruby-runtime/lib/jsii/utils/core_ext.rb

@@ -10,8 +10,9 @@
 #   - `Jsii::Utils`        — string helpers (`underscore`, `camelize`, `blank?`).
 #   - `Jsii::Serializer`   — explicit wire-format `dump` / `load`.
 #
-# The file is kept (empty) so existing `require 'jsii/utils/core_ext'` paths
-# continue to load.  Do NOT re-introduce monkey-patches here.
+# The file remains patch-free but intentionally loads `Jsii::Utils` and
+# `Jsii::Serializer` so existing `require 'jsii/utils/core_ext'` paths
+# continue to load backward-compatibly.  Do NOT re-introduce monkey-patches here.
 
 require_relative '../utils'
 require_relative '../serializer'