spec/ruby/core/hash/constructor_spec.rb: add "ruby_version_is" guard

follow up for d3f1c615c5

spec/ruby/core/hash/constructor_spec.rb

@@ -42,13 +42,26 @@ describe "Hash.[]" do
     Hash[ary].should == { a: :b }
   end
 
-  it "ignores elements that are not arrays" do
-    -> {
-      Hash[[:a]].should == {}
-    }.should raise_error(ArgumentError)
-    -> {
-      Hash[[:nil]].should == {}
-    }.should raise_error(ArgumentError)
+  ruby_version_is "" ... "2.7" do
+    it "ignores elements that are not arrays" do
+      -> {
+        Hash[[:a]].should == {}
+      }.should complain(/ignoring wrong elements/)
+      -> {
+        Hash[[:nil]].should == {}
+      }.should complain(/ignoring wrong elements/)
+    end
+  end
+
+  ruby_version_is "2.7" do
+    it "ignores elements that are not arrays" do
+      -> {
+        Hash[[:a]].should == {}
+      }.should raise_error(ArgumentError)
+      -> {
+        Hash[[:nil]].should == {}
+      }.should raise_error(ArgumentError)
+    end
   end
 
   it "raises an ArgumentError for arrays of more than 2 elements" do