Upgrade elasticsearch-rest-client to 6.5.3
Upgrade elasticsearch-rest-client to 6.5.3

According to the release notes [1] there are no client changes. This is
just to keep up-to-date with the latest release.

[1] https://www.elastic.co/guide/en/elasticsearch/reference/current/release-notes-6.5.3.html

Change-Id: I2878451d9e6f146e83779a3b639346828b50b0ca

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