enh: show cropped calendar popup

[enjeck]

Calendar was hidden if the modal wasn't long enough. This PR ensures it isn't cropped.

Before

After

[juliusknorr]

I think this approach would cause the overflow scrolling of modals to break but should not longer be necessary with the migration to the native date time picker with #647

[enjeck]

After #647, we no longer need this :)

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