Add version guard

Author: eregon

core/numeric/clone_spec.rb

@@ -23,8 +23,10 @@
     -> { 1.clone(freeze: false) }.should raise_error(ArgumentError, /can't unfreeze/)
   end
 
-  it "does not change frozen status if passed freeze: nil" do
-    value = 1
-    value.clone(freeze: nil).should equal(value)
+  ruby_version_is "3.0" do
+    it "does not change frozen status if passed freeze: nil" do
+      value = 1
+      value.clone(freeze: nil).should equal(value)
+    end
   end
 end