Add license type: BSD is NOTICE license

Bug: 68860345
Bug: 69058154
Bug: 151953481

Test: no code changes
Change-Id: I3ca9e78cedc37b73ee88a6d106ab80336ce63a45
diff --git a/METADATA b/METADATA
index cfd2016..576db36 100644
--- a/METADATA
+++ b/METADATA
@@ -8,6 +8,7 @@
     type: GIT
     value: "https://github.com/golang/protobuf"
   }
+  license_type: NOTICE
   version: "v1.3.5"
   last_upgrade_date {
     year: 2020