don't describe removed usage of Yaml::parse()

Author: xabbuh

components/yaml/introduction.rst

@@ -138,12 +138,6 @@ string or a file containing YAML. Internally, it calls the
 :method:`Symfony\\Component\\Yaml\\Parser::parse` method, but enhances the
 error if something goes wrong by adding the filename to the message.
 
-.. caution::
-
-    Because it is currently possible to pass a filename to this method, you
-    must validate the input first. Passing a filename is deprecated in
-    Symfony 2.2, and will be removed in Symfony 3.0.
-
 .. _components-yaml-dump:
 
 Writing YAML Files