psql offered USING, WHERE, and SET in this context, but SET is not a valid
possibility here.  Seems to have been a thinko in commit 
f5ab0a14ea83eb6c
which added DELETE's USING option.
        COMPLETE_WITH_SCHEMA_QUERY(Query_for_list_of_updatables, NULL);
    /* Complete DELETE FROM <table> */
    else if (TailMatches3("DELETE", "FROM", MatchAny))
-       COMPLETE_WITH_LIST3("USING", "WHERE", "SET");
+       COMPLETE_WITH_LIST2("USING", "WHERE");
    /* XXX: implement tab completion for DELETE ... USING */
 
 /* DISCARD */