makefile: fix goimports -local (#1763)

pkg/watch/notify_test.go

@@ -13,6 +13,7 @@ import (
 	"time"
 
 	"github.com/stretchr/testify/assert"
+
 	"github.com/windmilleng/tilt/internal/logger"
 	"github.com/windmilleng/tilt/internal/testutils/tempdir"
 )