Bug 1056316 - Prune out obsolete cases from error message about combining Throws with other things. r=bz

dom/bindings/parser/WebIDL.py

@@ -3197,8 +3197,7 @@ class IDLAttribute(IDLInterfaceMember):
               (identifier == "StoreInSlot" and
                (self.getExtendedAttribute("Throws") or
                 self.getExtendedAttribute("GetterThrows")))):
-            raise WebIDLError("Throwing things can't be [Pure] or [Constant] "
-                              "or [SameObject] or [StoreInSlot]",
+            raise WebIDLError("Throwing things can't be [StoreInSlot]",
                               [attr.location])
         elif identifier == "LenientThis":
             if not attr.noArguments():