Spell "Elasticsearch" correctly, not "ElasticSearch"

Summary: Ref T12450. These are like 95% my fault, but Elastic appears to spell the name "Elasticsearch" consistently in their branding.

Test Plan: grep ElasticSearch

Reviewers: chad, 20after4

Maniphest Tasks: T12450

Differential Revision: https://secure.phabricator.com/D17601