[design] Update default plugin auto-installation
[design] Update default plugin auto-installation

This updates the plugin auto-installation design page for DC/OS 1.13.

https://jira.mesosphere.com/browse/DCOS-46572

dcos/dcos-cli,kensipe/dcos-cli,kensipe/dcos-cli,dcos/dcos-cli,kensipe/dcos-cli,kensipe/dcos-cli,dcos/dcos-cli,dcos/dcos-cli,kensipe/dcos-cli,dcos/dcos-cli