debug/plan9obj: simplify s[:] to s where
debug/plan9obj: simplify s[:] to s where

Change-Id: Ib2eee1215ba046e4541af8afa3a921c680d2b37e
Reviewed-on: https://go-review.googlesource.com/c/142037
Run-TryBot: Iskander Sharipov <a698043bc2fd5ebc21d5b6bbc66ee53917362fef@intel.com>
TryBot-Result: Gobot Gobot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Iskander Sharipov <a698043bc2fd5ebc21d5b6bbc66ee53917362fef@intel.com>

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