math/rand: fix typo in comment
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 <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Trust: Alberto Donizetti <90b16103a35511ced020676f3544f17117fb4c92@gmail.com>

CAFxX/go,golang/go,nawawi/go,CAFxX/go,CAFxX/go,nawawi/go,CAFxX/go,cloudflare/go,nawawi/go,nawawi/go,cloudflare/go,golang/go,cloudflare/go,CAFxX/go,nawawi/go,CAFxX/go,golang/go,golang/go,golang/go,cloudflare/go,golang/go,CAFxX/go,nawawi/go,cloudflare/go,nawawi/go,cloudflare/go,cloudflare/go,CAFxX/go,nawawi/go,golang/go,cloudflare/go,golang/go