build(deps): bump watchdog from 6.0.0 to 7.0.0 in /tools/serve_header (#6048)

Bumps [watchdog](https://github.com/gorakhargosh/watchdog) from 6.0.0 to 7.0.0.
- [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/v6.0.0...v7.0.0)

---
updated-dependencies:
- dependency-name: watchdog
  dependency-version: 7.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

tools/serve_header/requirements.txt

@@ -1,2 +1,2 @@
 PyYAML==6.0.3
-watchdog==6.0.0
+watchdog==7.0.0