Commit 3f1a89c7dd changed most of the
install docs to use "Default" instead of "default" for project/user
domain names according to the keystone docs, but the install doc for
PyPI has been missed. This patch fixes it accordingly.
Change-Id: I2e92730ff5819bf49cf1b286356870fdb9c6ece5
Story: #2006652
Task: #36894