warn to throw ES response headers not working everywhere

[sckott]

via #260

x <- connect(errors = "complete")
if (index_exists(x, "foobar")) index_delete(x, "foobar")
df <- data.frame(name = letters[1:3], size = 1:3, id = 100:102)
invisible(docs_bulk(x, df, 'foobar', 'foobar', es_ids = FALSE, verbose = TRUE))

#> < HTTP/1.1 200 OK
#> < Warning: 299 Elasticsearch-7.2.0-508c38a "[types removal] Specifying types in bulk requests is deprecated."
#> < content-type: application/json; charset=UTF-8
#> < content-encoding: gzip
#> < content-length: 202

i think perhaps I just didn't implement this throughout pkg yet, or maybe the warning string pattern changed