pep440: remove redundant `without_local()` (#2019)
In this context, we already know (as the comment says) that `self` does
not have a local segment, so we don't need to strip it.
This change isn't motivated by anything other than making the code and
comment in sync. For example, when I first looked at it, I wondered
whether the extra stripping was somehow necessary. But it isn't.
