Update spec/function.dd

Co-authored-by: Max Haughton <maxhaton@gmail.com>

Author: dkorpel

spec/function.dd

@@ -1939,7 +1939,7 @@ $(H3 $(LNAME2 ref-return-scope-parameters, Ref Return Scope Parameters))
 
         $(P It is not possible to have both `return ref` and `return scope` semantics
         for the same parameter.
-        When a parameter is passed by `ref` and has both the `return` and `scope` attributes,
+        When a parameter is passed by `ref` and has both the `return` and `scope` storage classes,
         it gets $(LINK2 #return-scope-parameters, `return scope`) semantics if and only if the `return` and `scope`
         keywords appear adjacent to each other, in that order.
         In all other cases, the parameter has $(LINK2 #return-ref-parameters, `return ref`) semantics