testing: documentation typo: s;benchark;benchmark;

[rolandosegura]

Documentation of package testing on section about benchmark says:

src/pkg/testing.go:47:// During benchark execution, b.N is adjusted until the benchmark function lasts

What did you expect to see?

During benchmark execution, b.N ...

What did you see instead?

During benchark execution, b.N ...

What version of Go are you using (go version)?

; go version
go version go1.4.2 darwin/amd64