security/veracrypt: unbreak build with wxWidgets 3.0.3

TextUserInterface.cpp:122:5: error: const_cast from 'const wxScopedWCharBuffer' (aka 'const wxScopedCharTypeBuffer<wchar_t>') to 'wchar_t *' is not allowed

const_cast <wchar_t *> (passwordStr.wc_str())[i] = L'X';
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

PR: 223758
Submitted by: rozhuk.im@gmail.com
Approved by: maintainer timeout (2 months)