Bump cdav-library from `a41be4f` to `a9642c7`

Bumps [cdav-library](https://github.com/nextcloud/cdav-library) from `a41be4f` to `a9642c7`.
- [Release notes](https://github.com/nextcloud/cdav-library/releases)
- [Commits](https://github.com/nextcloud/cdav-library/compare/a41be4f7c4793ce9b681151ad33dc872989e701d...a9642c7c83db37120f8c74306c7e761f3e78524d

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