test/ken/slicearray.go: correct type width in comment
test/ken/slicearray.go: correct type width in comment

The type was changed in https://golang.org/cl/3991043 but the comment
wasn't updated.

Change-Id: I7ba3f625c732e5e801675ffc5d4a28e1d310faa3
Reviewed-on: https://go-review.googlesource.com/c/go/+/369374
Trust: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
Run-TryBot: Ian Lance Taylor <87e9c6d529889242b7e184afb632328636553ab4@golang.org>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>

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