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
1 file changed