doc/go1.15: 1.15 supports OpenBSD 6.7 on arm and arm64
doc/go1.15: 1.15 supports OpenBSD 6.7 on arm and arm64

Change-Id: Ibea6fbb73abdb7201855e80967120c07484d6460
Reviewed-on: https://go-review.googlesource.com/c/go/+/236557
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

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