cmGlobalVisualStudioGenerator: Fix compiling as C++20 in VS 2022

Adding missing narrow string conversion.

This backports commit f3c918ef1b (cmGlobalVisualStudioGenerator: Fix
compiling as C++20 in VS 2022, 2022-10-20, v3.25.0-rc3~31^2) to the
CMake 3.23 and 3.24 branches.

Fixes: #24162

Source/cmGlobalVisualStudioGenerator.cxx

@@ -630,7 +630,8 @@ bool IsVisualStudioMacrosFileRegistered(const std::string& macrosFile,
 
         RegCloseKey(hsubkey);
       } else {
-        std::cout << "error opening subkey: " << subkeyname << std::endl;
+        std::cout << "error opening subkey: "
+                  << cmsys::Encoding::ToNarrow(subkeyname) << std::endl;
         std::cout << std::endl;
       }