Bump watchdog from 2.1.6 to 4.0.1 in /requirements

Bumps [watchdog](https://github.com/gorakhargosh/watchdog) from 2.1.6 to 4.0.1.
- [Release notes](https://github.com/gorakhargosh/watchdog/releases)
- [Changelog](https://github.com/gorakhargosh/watchdog/blob/master/changelog.rst)
- [Commits](gorakhargosh/watchdog@v2.1.6...v4.0.1)

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

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

Author: dependabot[bot]

requirements/dev.txt

@@ -1,3 +1,3 @@
 -r common.txt
 pre-commit~=2.20.0
-watchdog==2.1.6
+watchdog==4.0.1