update OTA script in tm-mainline-prod to the latest version.

The last change in tm-mainline-prod was last year (aosp/2040556), did a copy of current version in udc-dev.

Test: local ota
Bug: 279622634
Change-Id: I6563122f21d7213bfa7200e28cdfa69bd95aa3e2
Merged-In: Iaa317a3a4b8addbca8ea987aee9953c78fa1a679
diff --git a/scripts/update_payload/checker.py b/scripts/update_payload/checker.py
index 56a9370..44b6811 100644
--- a/scripts/update_payload/checker.py
+++ b/scripts/update_payload/checker.py
@@ -42,7 +42,7 @@
 from update_payload import error
 from update_payload import format_utils
 from update_payload import histogram
-from update_payload import update_metadata_pb2
+import update_metadata_pb2
 
 #
 # Constants.