Bump elasticsearch from 6.1.1 to 7.0.4

Bumps [elasticsearch](https://github.com/elastic/elasticsearch-py) from 6.1.1 to 7.0.4.
- [Release notes](https://github.com/elastic/elasticsearch-py/releases)
- [Changelog](https://github.com/elastic/elasticsearch-py/blob/7.0.4/Changelog.rst)
- [Commits](elastic/elasticsearch-py@6.1.1...7.0.4)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

requirements.txt

@@ -5,7 +5,7 @@ certifi==2017.7.27.1
 chardet==3.0.4
 click==7.0
 dominate==2.4.0
-elasticsearch==6.1.1
+elasticsearch==7.0.4
 Flask==1.1.1
 Flask-Babel==0.12.2
 Flask-Bootstrap==3.3.7.1