Remove outdated comment in operations.prepare
Remove outdated comment in operations.prepare

There are several reasons why we don't trace progress as indicated a few
lines above.

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