dashboard: set GOPROXY=off for the "go" repo to catch more network usage
dashboard: set GOPROXY=off for the "go" repo to catch more network usage

Updates golang/go#30612
Updates golang/go#30760

Change-Id: I296f4f7a163c1bdd59e839229c0961b21f26da89
Reviewed-on: https://go-review.googlesource.com/c/build/+/167039
Reviewed-by: Bryan C. Mills <1c8aad60184261ccede67f5c63a0d2a3bf3c9ff4@google.com>

golang/build,golang/build,golang/build,golang/build