build(deps): bump structlog from 21.1.0 to 21.5.0 in /tools

Bumps [structlog](https://github.com/hynek/structlog) from 21.1.0 to 21.5.0.
- [Release notes](https://github.com/hynek/structlog/releases)
- [Changelog](https://github.com/hynek/structlog/blob/main/CHANGELOG.rst)
- [Commits](hynek/structlog@21.1.0...21.5.0)

---
updated-dependencies:
- dependency-name: structlog
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

tools/requirements.txt

@@ -3,5 +3,5 @@ async-timeout==3.0.1
 logbook==1.5.3
 pytz==2021.1
 raven==6.10.0
-structlog==21.1.0
+structlog==21.5.0
 taskcluster==44.2.2