minor #17055 [Form] Allow TranslatableInterface to the FormType help option (alamirault)

This PR was merged into the 6.2 branch.

Discussion
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[Form] Allow TranslatableInterface to the FormType help option

Symfony PR: symfony/symfony#47050

Supports TranslatableInterface FormType help option.

Commits
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959bc5e [Form] Allow TranslatableInterface to the FormType help option

Author: javiereguiluz

reference/forms/types/options/help.rst.inc

@@ -1,7 +1,7 @@
 help
 ~~~~
 
-**type**: ``string`` or ``TranslatableMessage`` **default**: null
+**type**: ``string`` or ``TranslatableInterface`` **default**: null
 
 Allows you to define a help message for the form field, which by default is
 rendered below the field::