Revert "Use D8 by default for android_test"

This reverts commit 02edc1004757f6d6d5c2e2a93f1e8656ae2435cf.

Reason for revert: Breaks test_suites_x86_64_coverage

Bug: 233421462
Change-Id: I7b04d3fd7802be0f271ea3c29ef25e3d08ab1389
diff --git a/java/java_test.go b/java/java_test.go
index 56a4248..4c93824 100644
--- a/java/java_test.go
+++ b/java/java_test.go
@@ -723,9 +723,9 @@
 		t.Errorf("atestNoOptimize should not optimize APK")
 	}
 
-	atestDefault := ctx.ModuleForTests("atestDefault", "android_common").MaybeRule("d8")
+	atestDefault := ctx.ModuleForTests("atestDefault", "android_common").MaybeRule("r8")
 	if atestDefault.Output == nil {
-		t.Errorf("atestDefault should not optimize APK")
+		t.Errorf("atestDefault should optimize APK")
 	}
 }