Remove debug from calendar field as it breaks saving to the DB

[wilsonge]

Fixes #19607

When you have language debug enabled the calendar dates will not save to the db as they are in the incorrect format. We can't show these in debug mode. This is similar to the fix for e.g in the template adapter.

Note in 4.x this gives an error correctly but in 3.x will silently insert an empty string to the db

[brianteeman]

I have tested this item ✅ successfully on 9474e5a

---

_{This comment was created with the J!Tracker Application at issues.joomla.org/tracker/joomla-cms/21717.}