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://golang.org/cl/13393045

src/pkg/regexp/exec_test.go

@@ -689,7 +689,7 @@ func BenchmarkMatchEasy1_1K(b *testing.B)   { benchmark(b, easy1, 1<<10) }
 func BenchmarkMatchEasy1_32K(b *testing.B)  { benchmark(b, easy1, 32<<10) }
 func BenchmarkMatchEasy1_1M(b *testing.B)   { benchmark(b, easy1, 1<<20) }
 func BenchmarkMatchEasy1_32M(b *testing.B)  { benchmark(b, easy1, 32<<20) }
-func BenchmarkMatchMedium_32(b *testing.B)  { benchmark(b, medium, 1<<0) }
+func BenchmarkMatchMedium_32(b *testing.B)  { benchmark(b, medium, 32<<0) }
 func BenchmarkMatchMedium_1K(b *testing.B)  { benchmark(b, medium, 1<<10) }
 func BenchmarkMatchMedium_32K(b *testing.B) { benchmark(b, medium, 32<<10) }
 func BenchmarkMatchMedium_1M(b *testing.B)  { benchmark(b, medium, 1<<20) }