Bump elasticsearch from 6.3.1 to 7.6.0

Bumps [elasticsearch](https://github.com/elastic/elasticsearch-py) from 6.3.1 to 7.6.0.
- [Release notes](https://github.com/elastic/elasticsearch-py/releases)
- [Changelog](https://github.com/elastic/elasticsearch-py/blob/7.6.0/Changelog.rst)
- [Commits](elastic/elasticsearch-py@6.3.1...7.6.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

requirements.txt

@@ -7,7 +7,7 @@ colorama==0.4.1
 cornice==3.5.1
 cornice-swagger==0.7.0
 dockerflow==2018.4.0
-elasticsearch==6.3.1
+elasticsearch==7.6.0
 hupper==1.6.1
 idna==2.8
 iso8601==0.1.12