add missing dot

Author: xabbuh

reference/forms/types/collection.rst

@@ -341,7 +341,7 @@ This is the field type for each item in this collection (e.g. ``TextType``,
 ``ChoiceType``, etc). For example, if you have an array of email addresses,
 you'd use the :doc:`EmailType </reference/forms/types/email>`. If you want
 to embed a collection of some other form, pass the form type class as this
-option (e.g. ``MyFormType::class``)
+option (e.g. ``MyFormType::class``).
 
 prototype
 ~~~~~~~~~