[#2927] Adding missing word thanks to @xabbuh

Author: weaverryan

cookbook/form/dynamic_form_modification.rst

@@ -459,7 +459,7 @@ On a form, we can usually listen to the following events:
 
 .. versionadded:: 2.2.6
 
-    The behavior of the ``POST_BIND`` changed slightly in 2.2.6, which the
+    The behavior of the ``POST_BIND`` event changed slightly in 2.2.6, which the
     below example uses.
 
 The key is to add a ``POST_BIND`` listener to the field that your new field