go.text/internal/triegen: block 3 should be 2, counted from 0, as blocks are refered to elsewhere.
go.text/internal/triegen: block 3 should be 2, counted from 0, as blocks are
refered to elsewhere.

LGTM=nigeltao
R=nigeltao
CC=golang-codereviews
https://golang.org/cl/132130043

cmars/tools,golang/text,cmars/tools,cmars/tools,npchp110/text,cmars/tools