design: fix broken link in vgo proposal
design: fix broken link in vgo proposal

Change-Id: I78fffe37d16a33d33f7bb9e81fd5d26386296f08
GitHub-Last-Rev: 8dd0586fc9052eb5c94e8fccbda4fbd26d3cfebc
GitHub-Pull-Request: golang/proposal#11
Reviewed-on: https://go-review.googlesource.com/102475
Reviewed-by: Brad Fitzpatrick <ae9783c0b0efc69cd85ab025ddd17aa44cdc4aa5@golang.org>

golang/proposal,golang/proposal