bug #19314 [Constraints] Update callback argument type (alexandre-daubois)

This PR was merged into the 6.4 branch.

Discussion
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[Constraints] Update `callback` argument type

Fix #19313

Commits
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66b1662 [Constraints] Update `callback` argument type

Author: OskarStark

reference/constraints/Choice.rst

@@ -262,7 +262,7 @@ Available Options
 ``callback``
 ~~~~~~~~~~~~
 
-**type**: ``string|array|Closure``
+**type**: ``callable|string|null`` **default**: ``null``
 
 This is a callback method that can be used instead of the `choices`_ option
 to return the choices array. See