Add license type: Apache2 is a NOTICE license

Bug: 68860345
Bug: 69058154
Bug: 151953481

Test: no code changes
Change-Id: I56ad0f531f135db5007723bc118ca8a5f2d76912
diff --git a/METADATA b/METADATA
index 673bc9c..d633669 100644
--- a/METADATA
+++ b/METADATA
@@ -10,6 +10,7 @@
     value: "https://github.com/square/javapoet.git"
   }
   version: "javapoet-1.12.1"
+  license_type: NOTICE
   last_upgrade_date {
     year: 2020
     month: 2