Bump watchdog from 0.9.0 to 3.0.0

Bumps [watchdog](https://github.com/gorakhargosh/watchdog) from 0.9.0 to 3.0.0.
- [Release notes](https://github.com/gorakhargosh/watchdog/releases)
- [Changelog](https://github.com/gorakhargosh/watchdog/blob/master/changelog.rst)
- [Commits](gorakhargosh/watchdog@v0.9.0...v3.0.0)

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

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

Author: dependabot[bot]

requirements_dev.txt

@@ -12,5 +12,5 @@ pytest_cov==2.7.1
 Sphinx==2.2.0
 sphinx_rtd_theme==0.4.3
 bumpversion==0.5.3
-watchdog==0.9.0
+watchdog==3.0.0
 pytest-runner==6.0.0