regexp: fix a benchmark case
regexp: fix a benchmark case

I noticed that this one benchmark in particular was very
noisy.  Looking into it, I saw that the table was wrong
and inconsistent with the lines above and below.

R=golang-dev, crawshaw
CC=golang-dev
https://codereview.appspot.com/13393045

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang