Removed 'Fields' from documentation for 'Interface' because Interfaces cannot have fields.

modules/monkey/newdocs/language/user-types.md

@@ -66,7 +66,7 @@ To declare an interface:
 
 _Interfaces_ is a comma separated list of interface types.
 
-An interface can contain consts, globals, fields, methods, functions and other user defined types.
+An interface can contain consts, globals, methods, functions and other user defined types.
 
 Interface methods are always 'abstract' and cannot declare any code.