Remove soong_metrics_proto from the import of the protobuf file.

No needed to define soong_metrics_proto since it is defined in
the Android.bp file.

Bug: b/172917718
Test: m nothing
Change-Id: Ib5f4cd6d06c08660803cf070da544e9c2d1dce1f
diff --git a/ui/metrics/metrics.go b/ui/metrics/metrics.go
index d46c89b..1cef2c7 100644
--- a/ui/metrics/metrics.go
+++ b/ui/metrics/metrics.go
@@ -23,7 +23,7 @@
 
 	"github.com/golang/protobuf/proto"
 
-	soong_metrics_proto "android/soong/ui/metrics/metrics_proto"
+	"android/soong/ui/metrics/metrics_proto"
 )
 
 const (