Add notice of requesting source code in ExtService s_minus apk

Flag: EXEMPT license change for b/418865751
Bug: 418865751
Test: presubmits
Change-Id: If51f286b65d9d7ce734404577e7ce7139a790ead
diff --git a/Android.bp b/Android.bp
index b7f24e8..81002d8 100644
--- a/Android.bp
+++ b/Android.bp
@@ -150,4 +150,8 @@
         "test_com.android.extservices",
     ],
     updatable: true,
+    licenses: [
+        "packages_modules_ExtServices_license",
+        "opensourcerequest",
+    ],
 }