Remove needless uses of wxString::c_str() in wxString::Format...

... and similar wx "variadics," which all treat wxString smartly enough that
you don't need this.

Don't need c_str either to convert wxString to const wxChar * because
wxString has a conversion operator that does the same.

src/LangChoice.cpp

@@ -128,10 +128,10 @@ void LangChoiceDialog::OnOk(wxCommandEvent & WXUNUSED(event))
       /* i18n-hint: The %s's are replaced by translated and untranslated
        * versions of language names. */
       msg.Printf(_("The language you have chosen, %s (%s), is not the same as the system language, %s (%s)."),
-                 mLangNames[ndx].c_str(),
-                 mLang.c_str(),
-                 sname.c_str(),
-                 slang.c_str());
+                 mLangNames[ndx],
+                 mLang,
+                 sname,
+                 slang);
       if (AudacityMessageBox(msg, _("Confirm"), wxYES_NO) == wxNO) {
          return;
       }