ada: Fix missing tag for with of an obsolescent function

Fix minor inconsistency in tags of warnings about obsolescent entities.

Part of cleaning up the warnings machinery to better handle references
to unset objects.

gcc/ada/

	* sem_warn.adb (Output_Obsolescent_Entity_Warnings): Tag warnings
	about obsolescent functions just like we tag similar warnings for
	packages and procedures.

gcc/ada/sem_warn.adb

@@ -3146,7 +3146,7 @@ package body Sem_Warn is
               ("?j?with of obsolescent procedure& declared#", N, E);
          else
             Error_Msg_NE
-              ("??with of obsolescent function& declared#", N, E);
+              ("?j?with of obsolescent function& declared#", N, E);
          end if;
 
       --  If we do not have a with clause, then ignore any reference to an