Bump tornado from 6.4.2 to 6.5.1

Bumps [tornado](https://github.com/tornadoweb/tornado) from 6.4.2 to 6.5.1.
- [Changelog](https://github.com/tornadoweb/tornado/blob/master/docs/releases.rst)
- [Commits](tornadoweb/tornado@v6.4.2...v6.5.1)

---
updated-dependencies:
- dependency-name: tornado
  dependency-version: 6.5.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

requirements_mapping.txt

@@ -42,7 +42,7 @@ pytz==2020.4
 PyYAML==5.4
 Shapely==1.7.1
 six==1.15.0
-tornado==6.4.2
+tornado==6.5.1
 traitlets
 typing-extensions==3.7.4.3
 wcwidth==0.2.5