Remove no longer necessary WinCmdLineArgs class

This change removes one use case of `std::wstring_convert`, which is
deprecated in C++17 and removed in C++26. Other uses remain for now.

src/bitcoin-cli.cpp

@@ -1328,10 +1328,6 @@ static int CommandLineRPC(int argc, char *argv[])
 
 MAIN_FUNCTION
 {
-#ifdef WIN32
-    common::WinCmdLineArgs winArgs;
-    std::tie(argc, argv) = winArgs.get();
-#endif
     SetupEnvironment();
     if (!SetupNetworking()) {
         tfm::format(std::cerr, "Error: Initializing networking failed\n");