[dependency] pin python-elasticsearch and python-elasticsearch-dsl versions as elasticsearch 7 has been released

Starting from ES6, `_type` metadata is deprecated,
cf. https://www.elastic.co/guide/en/elasticsearch/reference/current/removal-of-types.html

since it's a cube as package which are supported from there.

(closes #17071989)

Because version 5.0.0 depends on elasticsearch 5.0.0 and we
apparently do not want this as per parent changeset.