Bump tornado from 6.0.4 to 6.3.3 in /Python/covid_19

Bumps [tornado](https://github.com/tornadoweb/tornado) from 6.0.4 to 6.3.3.
- [Changelog](https://github.com/tornadoweb/tornado/blob/master/docs/releases.rst)
- [Commits](tornadoweb/tornado@v6.0.4...v6.3.3)

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

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

Python/covid_19/requirements.txt

@@ -64,7 +64,7 @@ six==1.15.0
 terminado==0.8.3
 testpath==0.4.4
 threadpoolctl==2.1.0
-tornado==6.0.4
+tornado==6.3.3
 traitlets==5.0.4
 wcwidth==0.2.5
 webencodings==0.5.1