Update Kibana installation instructions for Debian and RPM

See https://github.com/elastic/stack-docs/pull/198
The Getting started guide contains Kibana installation instructions here:
https://www.elastic.co/guide/en/elastic-stack-get-started/master/get-started-elastic-stack.html#install-kibana

The "deb or rpm" instructions use tar.gz files. They ought to be updated to match the specific instructions in https://www.elastic.co/guide/en/kibana/master/deb.html#install-deb and https://www.elastic.co/guide/en/kibana/master/rpm.html#install-rpm

Ideally the instructions can be re-used so they stay in synch