Add METADATA to test_serving: Apache2+MIT=NOTICE

Bug: 68860345
Bug: 69058154
Bug: 151953481

Test: no code changes

Exempt-From-Owner-Approval: janitorial work

Change-Id: I551a7f8a12563b189c89452f57ade6444e4d7f8b

METADATA

+third_party {
+  license_type: NOTICE
+}