bytes: remove obsolete comment
bytes: remove obsolete comment

Change-Id: Iec4348eb674c8c64497c82e5d7cd656736cfcebd
GitHub-Last-Rev: 462c323960be0ca1c126c051ab97f72949bdc2b6
GitHub-Pull-Request: golang/go#32225
Reviewed-on: https://go-review.googlesource.com/c/go/+/178797
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

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