Rename product_services to system_ext

Bug: 134359158
Test: build and check if system_ext.img is created
Change-Id: Ice3229baf97a94c24a6eea22e7d4571941d7f843
diff --git a/cmd/diff_target_files/target_files.go b/cmd/diff_target_files/target_files.go
index 8705ca7..0fa04e8 100644
--- a/cmd/diff_target_files/target_files.go
+++ b/cmd/diff_target_files/target_files.go
@@ -28,7 +28,7 @@
 	"ODM/",
 	"OEM/",
 	"PRODUCT/",
-	"PRODUCT_SERVICES/",
+	"SYSTEM_EXT/",
 	"ROOT/",
 	"SYSTEM/",
 	"SYSTEM_OTHER/",