Documentation fixes (#4831)
Documentation fixes (#4831)

- Wheel doesn't have a public API
- Reword warning about installing into a running interpreter

pradyunsg/pip,zvezdan/pip,pfmoore/pip,pradyunsg/pip,zvezdan/pip,techtonik/pip,techtonik/pip,RonnyPfannschmidt/pip,sbidoul/pip,rouge8/pip,pypa/pip,pfmoore/pip,pypa/pip,zvezdan/pip,xavfernandez/pip,RonnyPfannschmidt/pip,techtonik/pip,rouge8/pip,RonnyPfannschmidt/pip,rouge8/pip,xavfernandez/pip,sbidoul/pip,xavfernandez/pip