Remove date popups on the visit page when cursor doesn't point it anymore

On the calendar shown on https://archive.softwareheritage.org/browse/origin/visits/?origin_url=https://nix-community.github.io/nixpkgs-swh/sources-unstable.json , a popup is displayed when my cursor points on a visit date. Since the popup hides all other dates, I need to wait for a timeout to get this popup removed.

This popup should only be displayed when the cursor points to it.

Migrated from T2426 (view on Phabricator)

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