Bump webdav from 3.6.2 to 4.0.0

Bumps [webdav](https://github.com/perry-mitchell/webdav-client) from 3.6.2 to 4.0.0.
- [Release notes](https://github.com/perry-mitchell/webdav-client/releases)
- [Changelog](https://github.com/perry-mitchell/webdav-client/blob/master/CHANGELOG.md)
- [Commits](https://github.com/perry-mitchell/webdav-client/compare/v3.6.2...v4.0.0

)

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