[Feature #15408] Fix up _id2ref_spec.rb

spec/ruby/core/objectspace/_id2ref_spec.rb

@@ -1,6 +1,18 @@
 require_relative '../../spec_helper'
 
-describe "ObjectSpace._id2ref" do
+ruby_version_is "3.5" do
+  describe "ObjectSpace._id2ref" do
+    it "is deprecated" do
+      id = nil.object_id
+      -> {
+        ObjectSpace._id2ref(id)
+      }.should complain(/warning: ObjectSpace\._id2ref is deprecated/)
+    end
+  end
+end
+
+ruby_version_is ""..."3.5" do
+  describe "ObjectSpace._id2ref" do
     it "converts an object id to a reference to the object" do
       s = "I am a string"
       r = ObjectSpace._id2ref(s.object_id)
@@ -49,4 +61,5 @@ describe "ObjectSpace._id2ref" do
     it 'raises RangeError when an object could not be found' do
       proc { ObjectSpace._id2ref(1 << 60) }.should raise_error(RangeError)
     end
+  end
 end