math/rand: fix typo in comment

Change-Id: I57fbabf272bdfd61918db155ee6f7091f18e5979
GitHub-Last-Rev: e138804b1ab8086b3742861873b077d6cca8108a
GitHub-Pull-Request: golang/go#43495
Reviewed-on: https://go-review.googlesource.com/c/go/+/281373
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Trust: Alberto Donizetti <alb.donizetti@gmail.com>

src/math/rand/gen_cooked.go

@@ -4,7 +4,7 @@
 
 // +build ignore
 
-// This program computes the value of rng_cooked in rng.go,
+// This program computes the value of rngCooked in rng.go,
 // which is used for seeding all instances of rand.Source.
 // a 64bit and a 63bit version of the array is printed to
 // the standard output.