Bump calendar-js from `6e87c42` to `fbfbcc8`

Bumps [calendar-js](https://github.com/nextcloud/calendar-js) from `6e87c42` to `fbfbcc8`.
- [Release notes](https://github.com/nextcloud/calendar-js/releases)
- [Commits](https://github.com/nextcloud/calendar-js/compare/6e87c42e07c887f1695d450cfa2ee34290b068d4...fbfbcc8c3f51998d5b9937e986fd43268d7e7098

)

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