build(deps): bump structlog from 20.2.0 to 21.1.0 in /tools

Bumps [structlog](https://github.com/hynek/structlog) from 20.2.0 to 21.1.0.
- [Release notes](https://github.com/hynek/structlog/releases)
- [Changelog](https://github.com/hynek/structlog/blob/main/CHANGELOG.rst)
- [Commits](hynek/structlog@20.2.0...21.1.0)

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

Author: dependabot[bot]

tools/requirements.txt

@@ -2,5 +2,5 @@ aiohttp==3.7.3
 async-timeout==3.0.1
 logbook==1.5.3
 raven==6.10.0
-structlog==20.2.0
+structlog==21.1.0
 taskcluster==40.0.3