Update File.rst

Replace mimeTypes parameters by "extension" and "extensions" in extensionMessage option

Author: corentingd

reference/constraints/File.rst

@@ -314,7 +314,12 @@ Parameter                       Description
 The message displayed if the extension of the file is not a valid extension
 per the `extensions`_ option.
 
-.. include:: /reference/constraints/_parameters-mime-types-message-option.rst.inc
+==================== ==============================================================
+Parameter            Description
+==================== ==============================================================
+``{{ extension }}``  The extension of the given file
+``{{ extensions }}`` The list of allowed file extensions
+==================== ==============================================================
 
 ``mimeTypesMessage``
 ~~~~~~~~~~~~~~~~~~~~