Use wxString::t_str() in calls to Windows API functions in wxMSW.

Use t_str() instead of wx_str() to make the code work correctly in UTF-8 build
in which wx_str() returns a pointer to UTF-8 buffer while we need a wchar_t
pointer for Windows.

Closes #14371.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@71640 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/msw/utilsgui.cpp

@@ -373,7 +373,7 @@ bool wxLaunchDefaultApplication(const wxString& document, int flags)
     wxUnusedVar(flags);
 
     WinStruct<SHELLEXECUTEINFO> sei;
-    sei.lpFile = document.wx_str();
+    sei.lpFile = document.t_str();
 #ifdef __WXWINCE__
     sei.nShow = SW_SHOWNORMAL; // SW_SHOWDEFAULT not defined under CE (#10216)
 #else