cmd/go: remove inadvertent comment for vgo
cmd/go: remove inadvertent comment for vgo

This change was introduced while adding the dark copy
of golang.org/x/vgo in CL 118095.

While the comment made sense in a separate vgo repo, when it is
merged with the main repo, this should not remain.

Found while running mkalldocs.sh in CL 119695.

Change-Id: I112a4629c415032bd29e165ac1c27a0f3cabeede
Reviewed-on: https://go-review.googlesource.com/119938
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

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