Remove `InstallRequirement.uninstalled_pathset`
Remove `InstallRequirement.uninstalled_pathset`

Last actual usages of this were removed in #4642.

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