Bump tornado from 6.5.4 to 6.5.5 in /server

Bumps [tornado](https://github.com/tornadoweb/tornado) from 6.5.4 to 6.5.5.
- [Changelog](https://github.com/tornadoweb/tornado/blob/master/docs/releases.rst)
- [Commits](tornadoweb/tornado@v6.5.4...v6.5.5)

---
updated-dependencies:
- dependency-name: tornado
  dependency-version: 6.5.5
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Author: dependabot[bot]

server/requirements.txt

@@ -1,4 +1,4 @@
-tornado==6.5.4
+tornado==6.5.5
 sqlalchemy>=2.0.0,<2.1.0
 datetime==4.9
 python-dateutil==2.9.0.post0