Update bulk.ex with no types

[mrnovalles]

ElasticSearch 7.x [1] already described the removal of mapping types. For the case of bulk endpoints:

Types should also no longer appear in the body of requests. The following example of bulk indexing omits the type both in the URL, and in the individual bulk commands:

[1] https://www.elastic.co/guide/en/elasticsearch/reference/7.17/removal-of-types.html

This commit removes the /_doc/ part of the URL when making Bulk uploads as part of the hot_swap_index function.

Fixes #113

[lovebes]

@danielberkompas Can we merge this in somewhat urgently? Elasticsearch is already at 8.12, and removal of /_doc imho is a change that is due. On a bit of a selfish note I need this at my job ;)

For those that need to use the current url suffix can just use the older version of :elasticsearch.

[lovebes]

Actually #106 might be a better approach I think.