bytes: clean up a test
bytes: clean up a test

Change-Id: Iaa0e1721996b582bba9509c083755e1f125abb6b
GitHub-Last-Rev: c9b13ec0cdc2b22aafa54706dc6df6113a11712b
GitHub-Pull-Request: golang/go#29996
Reviewed-on: https://go-review.googlesource.com/c/160420
Run-TryBot: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Keith Randall <8c99c3a9284e493be632950b84cd789d08ed3e9d@golang.org>

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