Changed note to caution; reworded; changed deprecation version

Looking at the Symfony code, this was actually deprecated in 2.2. Move the warning text to the front because the validation warning is more important than the deprecation notice.

Author: jbafford

components/yaml/introduction.rst

@@ -134,13 +134,11 @@ 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.
 
-.. note::
+.. caution::
 
-    Although it is currently possible to pass the
-    :method:`Symfony\\Component\\Yaml\\Yaml::parse` static method a
-    filename, this functionality is deprecated in Symfony 2.3, and will be
-    removed in Symfony 3.0. Because it is possible to pass a filename, if
-    you use this method, you must validate the input first.
+    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.
 
 Executing PHP Inside YAML Files
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~