re_intuit_start(): remove other_last = rx_origin

re_intuit_start(): remove other_last = rx_origin

The previous commit made this assignment conditional on other_last
not decreasing; but it turns out that increasing it is pointless (although
harmless), since the next time round the "other" substring block, the
current rx_origin will be >= the old rx_origin (since we never decrease
it), and s >= new rx_origin. So s would already be >= the value we would set
other_last to, so it doesn't make any difference.