Elasticsearch: Remove support for EOL 6.7 version

As that version becomes EOL on September 26, 2020 [1].

In ElasticQueryAdapter, replace the former V6_7 constant use with a
comment preserving that information.

[1] https://www.elastic.co/support/eol

Change-Id: Ifaa6e61ab7e1178e71809b34ba2cc3602ab6794c
4 files changed
tree: 8954e9959f1ee73a90e3cc49d0d35f2be879c100
  1. java/
  2. javatests/