cmd/link: update comment for deadcode
cmd/link: update comment for deadcode

Update the comment to be in sync with the code.

Change-Id: I19586767a37347c4da1b4d3f7c6dc6cc2292a90f
Reviewed-on: https://go-review.googlesource.com/c/go/+/228877
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

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