Add mode: "test" to android.security.flags-aconfig-java-host

Test: CI

Bug: 309990433
Change-Id: I630782e0280be8687d55b5878da1a253c0f0be1a

AconfigFlags.bp

@@ -220,6 +220,7 @@ java_aconfig_library {
     name: "android.security.flags-aconfig-java-host",
     aconfig_declarations: "android.security.flags-aconfig",
     host_supported: true,
+    mode: "test",
     defaults: ["framework-minus-apex-aconfig-java-defaults"],
 }