Remove vendord cached_property

[oz123]

This is built in functool.cached_property since Python 3.8 and is redefined in many places we can import from without fearing it will be removed:

$ git grep -r "class cached_property"
pipenv/patched/notpip/_vendor/distlib/util.py:class cached_property(object):
pipenv/patched/notpip/_vendor/distro/distro.py:    class cached_property:  # type: ignore
pipenv/patched/notpip/_vendor/pyparsing/core.py:    class cached_property:
pipenv/vendor/cached_property.py:class cached_property(object):
pipenv/vendor/cached_property.py:class cached_property_with_ttl(object):
pipenv/vendor/distlib/util.py:class cached_property(object):