Bump calendar-js from `a5c9ef8` to `1c4fbb9`

Bumps [calendar-js](https://github.com/georgehrke/calendar-js) from `a5c9ef8` to `1c4fbb9`.
- [Release notes](https://github.com/georgehrke/calendar-js/releases)
- [Commits](https://github.com/georgehrke/calendar-js/compare/a5c9ef8369c398f58b18f7d6e1497c2a06a1d475...1c4fbb97e1d34981b658f8d2171bd488282cb62e

)

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