MINOR: remove quickstart-*.html (#313)

Both quickstart-docker.html and quickstart-zookeeper.html were added during the web-page redesign but were never finished. quickstart-docker.html is dangling and is removed in this PR. quickstart-zookeeper.html is use a actual quickstart and thus we rename it back to quickstart.html.

Cf apache/kafka#9721 for AK repo.
Also apache/kafka#9722

There is some difference between the old quickstart.html and the quickstart-zookeeper.html and I am not sure what is actually the correct quickstart?

Call for review @scott-confluent @guozhangwang @miguno

\cc @mimaison @bbejeck (to make sure we don't re-publish it during the release)

Reviewers: Guozhang Wang <wangguoz@gmail.com>, Scott Predmore <spredmore@confluent.io>, Bill Bejeck <bbejeck@apache.org>
11 files changed