Add license_type to METADATA: contains GPL=RESTRICTED

Bug: 68860345
Bug: 69058154
Bug: 151953481

Test: no code changes
Exempt-From-Owner-Approval: janitorial work
Change-Id: I4005f46ff6dfa65eca7bdb6d435d9dad2d33b1d4
diff --git a/METADATA b/METADATA
index 9414ff3..5363e12 100644
--- a/METADATA
+++ b/METADATA
@@ -10,6 +10,7 @@
     value: "https://github.com/facebook/zstd"
   }
   version: "v1.4.5"
+  license_type: RESTRICTED
   last_upgrade_date {
     year: 2020
     month: 6