runtime: remove zhangyunhao116/fastrand from cheaprand linkname comment
As of version 0.5.0 and Go 1.22 it no longer linknames cheaprand.
Fixes #67709
Change-Id: Ie00900e6428244fa1506bc509c265c10dc322f7a
Reviewed-on: https://go-review.googlesource.com/c/go/+/589555
Auto-Submit: Ian Lance Taylor <iant@golang.org> Reviewed-by: Michael Knyszek <mknyszek@google.com> Reviewed-by: Than McIntosh <thanm@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>