Update sabre/dav requirement from 4.2.0 to 4.2.1 in /build/integration

Update sabre/dav requirement from 4.2.0 to 4.2.1 in /build/integration

Updates the requirements on [sabre/dav](https://github.com/sabre-io/dav) to permit the latest version.
- [Release notes](https://github.com/sabre-io/dav/releases)
- [Changelog](https://github.com/sabre-io/dav/blob/master/CHANGELOG.md)
- [Commits](https://github.com/sabre-io/dav/compare/4.2.0...4.2.1)

---
updated-dependencies:
- dependency-name: sabre/dav
  dependency-type: direct:development
...

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