Elasticsearch indexing creates an empty index `notes`

Hello!

While working on https://gitlab.com/gitlab-com/infrastructure/issues/2157 we created the gitlab-production index with the following command:

vlopez@deploy:~$ sudo gitlab-rake gitlab:elastic:create_empty_index
Index created

After that, we enabled Elasticsearch indexing and Use experimental repository indexer on the admin settings console.

When documents started to be written in ES, another (empty) index notes was created too:

vlopez@elasticsearch01:~$ curl -s localhost:9200/_cat/indices
green open gitlab-production LHalf2VORvqCOMbKVcrZAQ 18 0 969754 115276 53.1gb 53.1gb
green open notes             asPz7JHLSlu09PTKMUigog  5 1      0      0  1.3kb   679b

Just for clarification, the notes index was not created after running sudo gitlab-rake gitlab:elastic:create_empty_index but after enabling indexing on the admin panel.

Confirmation that after a couple of hours is still empty:

vlopez@elasticsearch01:~$ curl -s localhost:9200/notes/_search?pretty
{
  "took" : 1,
  "timed_out" : false,
  "_shards" : {
    "total" : 5,
    "successful" : 5,
    "failed" : 0
  },
  "hits" : {
    "total" : 0,
    "max_score" : null,
    "hits" : [ ]
  }
}

I guess in some part of the code we are creating this index. This is not creating any kind of issue but it should be cleaned up.

Thanks a lot!!