Improve --ha description (was: typo in marathon document)

[chengweiv5]

https://mesosphere.github.io/marathon/docs/command-line-flags.html

v0.13.0 --[disable_]ha (Optional. Default: enabled): Run Marathon in HA mode with leader election. 
Allows starting an arbitrary number of other Marathons but all need to be started in HA mode. This mode 
requires a running ZooKeeper. See --master.

should be See --zk?

[philipnrmn]

Hi @chengweiv5,

I think See --master is correct here, because it explains the previous clause and the --master documentation is where we explain that ZooKeeper is optional. I'm not sure the reference adds all that much value though so maybe we should just remove it. What do you think?

[chengweiv5]

sure, good to me.