Use OutputFilesProvider on droidstubs

In the context of incremental soong, the output files
inter-module-communication will be through OutputFilesProvider.
The OutputFileProducer interface will be deprecated.

Test: CI
Bug: 339477385
Change-Id: I8ea7463cfc3881d800255aa99147897eeba85b04
diff --git a/java/droiddoc_test.go b/java/droiddoc_test.go
index 8d1f591..e584640 100644
--- a/java/droiddoc_test.go
+++ b/java/droiddoc_test.go
@@ -69,11 +69,7 @@
 			"bar-doc/a.java": nil,
 			"bar-doc/b.java": nil,
 		})
-	barStubs := ctx.ModuleForTests("bar-stubs", "android_common")
-	barStubsOutputs, err := barStubs.Module().(*Droidstubs).OutputFiles("")
-	if err != nil {
-		t.Errorf("Unexpected error %q retrieving \"bar-stubs\" output file", err)
-	}
+	barStubsOutputs := ctx.ModuleForTests("bar-stubs", "android_common").OutputFiles(t, "")
 	if len(barStubsOutputs) != 1 {
 		t.Errorf("Expected one output from \"bar-stubs\" got %s", barStubsOutputs)
 	}