[Ada] Change message format on missing return

gcc/ada/

	* sem_ch6.adb (Check_Returns): Change message on missing return.

gcc/ada/sem_ch6.adb

@@ -7760,7 +7760,7 @@ package body Sem_Ch6 is
                  ("RETURN statement missing following this statement<<!",
                   Last_Stm);
                Error_Msg_N
-                 ("\Program_Error ]<<!", Last_Stm);
+                 ("\Program_Error [<<!", Last_Stm);
             end if;
 
             --  Note: we set Err even though we have not issued a warning