QSaveFile[win]: remove fallback to old renameOverwrite

Our new way of doing it is atomic, so while conflicts can
still happen that leads to e.g. access denied, those will be
because the _target file_ is already accessed for some reason.
The fallback might be lucky enough that it happens after this
other access is done, but probably not. So remove the fallback
and just do the atomic rename.

Change-Id: I13f6b4b70974500b8dd9309138b9052b6a5acc62
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/io/qtemporaryfile.cpp

@@ -393,10 +393,9 @@ bool QTemporaryFileEngine::renameOverwrite(const QString &newName)
     }
 #ifdef Q_OS_WIN
     if (flags & Win32NonShared) {
-        if (d_func()->nativeRenameOverwrite(newName)) {
-            QFSFileEngine::close();
-            return true;
-        }
+        bool ok = d_func()->nativeRenameOverwrite(newName);
+        QFSFileEngine::close();
+        return ok;
     }
 #endif
     QFSFileEngine::close();