testing: fix copy/paste in docs

Follow-up to CL 36791.

Change-Id: I1c4831e5dfe90c205782e970ada7faff8a009daa
Reviewed-on: https://go-review.googlesource.com/36890Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/testing/benchmark.go

@@ -332,7 +332,7 @@ func (r BenchmarkResult) AllocsPerOp() int64 {
 	return int64(r.MemAllocs) / int64(r.N)
 }
 
-// AllocsPerOp returns r.MemBytes / r.N.
+// AllocedBytesPerOp returns r.MemBytes / r.N.
 func (r BenchmarkResult) AllocedBytesPerOp() int64 {
 	if r.N <= 0 {
 		return 0