Remove "index" param in Metricbeat config
Remove "index" param in Metricbeat config

Remove output.elasticsearch.index, because it is ignored when Index
Lifecycle Management is turned on (which it is, by default, and as we
have things configured).

Reference:
https://www.elastic.co/guide/en/beats/metricbeat/current/elasticsearch-output.html#index-option-es

mitodl/salt-ops,mitodl/salt-ops