Remove unused dependency_links variables in freeze.py.
Remove unused dependency_links variables in freeze.py.

rouge8/pip,rouge8/pip,xavfernandez/pip,pradyunsg/pip,xavfernandez/pip,pfmoore/pip,sbidoul/pip,pradyunsg/pip,sbidoul/pip,pypa/pip,pfmoore/pip,rouge8/pip,xavfernandez/pip,pypa/pip