Stop testing Elasticsearch 6.2 in periodic CI builds

Description

Elasticsearch 6.2 has been EOL for close to a year, and there are bugs that make it fail tests for sorts on double-nested fields (https://github.com/elastic/elasticsearch/issues/32130).

Same goes for older versions of 6.3, but we already don't test 6.3 because of other bugs.

Environment

None

Assignee

Yoann Rodière

Reporter

Yoann Rodière

Labels

None

Suitable for new contributors

None

Pull Request

None

Feedback Requested

None

Components

Fix versions

Priority

Major
Configure