bump up nested-table heuristic
bump up nested-table heuristic

this classififes nested tables in cleaneval set correctly as layout, even with
summary attributes that simply say the tables are for layout.

BUG=368941
R=yfriedman@chromium.org

Review URL: https://codereview.chromium.org/513613004

dalmirdasilva/dom-distiller,dalmirdasilva/dom-distiller,dalmirdasilva/dom-distiller,dalmirdasilva/dom-distiller,dalmirdasilva/dom-distiller