With the removal[*] of refs/publish in Gerrit 3.0.0, git-review
1.27.1 or later is needed to avoid attempting a push there and
ultimately failing. The git-review package in Ubuntu 18.04 LTS is
too old (1.26.0), so use latest from PyPI instead.

Adjust the quick-start document to install git-review with pip, and
on Debian/Ubuntu suggest including the python3-pip distro package
since it's split out separate from the interpreter packages.

[*] https://gerrit-review.googlesource.com/c/gerrit/+/192494

Change-Id: I247fb761667a99cf9f25478b49c5a1fe5d11a6cf