Bump cdav-library from `d3b96bf` to `c6e2e3b`

Bumps [cdav-library](https://github.com/nextcloud/cdav-library) from `d3b96bf` to `c6e2e3b`.
- [Release notes](https://github.com/nextcloud/cdav-library/releases)
- [Commits](https://github.com/nextcloud/cdav-library/compare/d3b96bff72fa24e6ba80e2c6ec0ce1ed098f1b77...c6e2e3b0daee965fa5d6db217d9020c67a977bf1

)

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