Improve styling of discovery snippet
Improve styling of discovery snippet

Original `discovery` snippet had a `curl` command that mentioned
multi-datacenter support. This removes part of the command that was
incorrect. It adds styling for the `dc2` section of the JSON output that
highlights the part of the query that relates to multiple data centers.

kingland/consul,youhong316/consul,youhong316/consul,scalp42/consul,scalp42/consul,kingland/consul,hashicorp/consul,vamage/consul,hashicorp/consul,kingland/consul,scalp42/consul,vamage/consul,youhong316/consul,42wim/consul,42wim/consul,vamage/consul,vamage/consul,42wim/consul,kingland/consul,hashicorp/consul,vamage/consul,youhong316/consul,42wim/consul,hashicorp/consul,kingland/consul,scalp42/consul,scalp42/consul,42wim/consul,youhong316/consul