merge choice_translation_domain files

Author: xabbuh

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

@@ -1,4 +1,12 @@
 choice_translation_domain
 ~~~~~~~~~~~~~~~~~~~~~~~~~
 
-.. include:: /reference/forms/types/options/_choice_translation_domain_body.rst.inc
+**type**: ``string``, ``boolean`` or ``null``
+
+This option determines if the choice values should be translated and in which
+translation domain.
+
+The values of the ``choice_translation_domain`` option can be ``true`` (reuse the current
+translation domain), ``false`` (disable translation), ``null`` (uses the parent translation
+domain or the default domain) or a string which represents the exact translation
+domain to use.