Fix ruby_testoptions on RubyCI

http://rubyci.s3.amazonaws.com/osx1200arm-no-yjit/ruby-master/log/20230308T185004Z.fail.html.gz

prelude.rb

@@ -27,5 +27,5 @@ module Enumerable
   # Makes a set from the enumerable object with given arguments.
   def to_set(klass = Set, *args, &block)
     klass.new(self, *args, &block)
-  end
+  end unless instance_methods.include?(:to_set) # RJIT could already load this from builtin prelude
 end