Bump elasticsearch from 7.6.0 to 7.7.0

Bumps [elasticsearch](https://github.com/elastic/elasticsearch-py) from 7.6.0 to 7.7.0.
- [Release notes](https://github.com/elastic/elasticsearch-py/releases)
- [Changelog](https://github.com/elastic/elasticsearch-py/blob/master/Changelog.rst)
- [Commits](elastic/elasticsearch-py@7.6.0...7.7.0)

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

requirements.txt

@@ -7,7 +7,7 @@ colorama==0.4.3
 cornice==4.0.1
 cornice-swagger==1.0.0
 dockerflow==2019.10.0
-elasticsearch==7.6.0
+elasticsearch==7.7.0
 hupper==1.10.2
 idna==2.9
 iso8601==0.1.12