chore: Bump watchdog from 1.0.2 to 4.0.0 in /docker

Bumps [watchdog](https://github.com/gorakhargosh/watchdog) from 1.0.2 to 4.0.0.
- [Release notes](https://github.com/gorakhargosh/watchdog/releases)
- [Changelog](https://github.com/gorakhargosh/watchdog/blob/master/changelog.rst)
- [Commits](https://github.com/gorakhargosh/watchdog/compare/v1.0.2...v4.0.0)

---
updated-dependencies:
- dependency-name: watchdog
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

docker/docker-requirements.txt

@@ -8,4 +8,4 @@ bcrypt==3.2.0
 # whatever bottle chooses as a default. Since the wsgiref server is not
 # production-ready, install waitress as a fallback for these cases.
 waitress==2.1.2
-watchdog==1.0.2
+watchdog==4.0.0