exec hof mod vendor

exec hof mod get github.com/hofstadter-io/hof@v0.6.8-rc.6

-- cue.mod/module.cue --
module: "hof.io/test"
cue:    "0.8.2"

require: {
	"github.com/hofstadter-io/hof": "v0.6.8"
}
