doc/go1.18: mention bytes.Cut and strings.Cut
doc/go1.18: mention bytes.Cut and strings.Cut

For #47694.

Updates #46336.

Change-Id: Ibbd058a1fd4d6b0aa38d3e8dc15b560d1e149f7e
Reviewed-on: https://go-review.googlesource.com/c/go/+/369981
Trust: Austin Clements <7ea35d812706d9213868749011af1ed4fa2f6aa0@google.com>
Reviewed-by: Jeremy Faller <b3f594e10a9edcf5413cf1190121d45078c62290@golang.org>

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