Bump tornado from 6.5.7 to 6.5.8 in /server (#1319)

Bumps [tornado](https://github.com/tornadoweb/tornado) from 6.5.7 to 6.5.8.
- [Changelog](https://github.com/tornadoweb/tornado/blob/master/docs/releases.rst)
- [Commits](tornadoweb/tornado@v6.5.7...v6.5.8)

---
updated-dependencies:
- dependency-name: tornado
  dependency-version: 6.5.8
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Tim Bradgate <timbradgate@hotmail.co.uk>

Author: dependabot[bot]

server/requirements.txt

@@ -1,4 +1,4 @@
-tornado==6.5.7
+tornado==6.5.8
 sqlalchemy>=2.0.51,<2.1.0
 python-dateutil==2.9.0.post0
 marshmallow-sqlalchemy>=1.5.0