dashboard: fix vet warning
dashboard: fix vet warning

Fix warning reported by "go vet":

./builders.go:1126:11: golang.org/x/build/types.MajorMinor struct literal uses unkeyed fields
./builders.go:1506:8: golang.org/x/build/types.MajorMinor struct literal uses unkeyed fields

Change-Id: Ifa167bdcda4eb6123362353da58307dfb94174df
Reviewed-on: https://go-review.googlesource.com/c/build/+/423034
Reviewed-by: Heschi Kreinick <e89ab2b172855aa0ad01c40c4d8a3535a61ac68a@google.com>
Reviewed-by: Dmitri Shuralyov <d181b7fea0ec87c86ba5a890ab716db52498e3ba@golang.org>

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