[1.7.x] Fixed #22613 -- Added formfield_for_choice_field() to the list of…

[1.7.x] Fixed #22613 -- Added formfield_for_choice_field() to the list of methods that InlineModelAdmin supports.

Backport of 986bd41f from master

docs/ref/contrib/admin/index.txt

@@ -1927,6 +1927,7 @@ adds some of its own (the shared features are actually defined in the
 - :attr:`~ModelAdmin.radio_fields`
 - :attr:`~ModelAdmin.readonly_fields`
 - :attr:`~InlineModelAdmin.raw_id_fields`
+- :meth:`~ModelAdmin.formfield_for_choice_field`
 - :meth:`~ModelAdmin.formfield_for_foreignkey`
 - :meth:`~ModelAdmin.formfield_for_manytomany`
 - :meth:`~ModelAdmin.has_add_permission`