ObjPtr<>-ify ClassLinker::FindClass(), fix 1 stale reference use.

Thread::CreateAnnotatedStackTrace() was using a stale
reference `aste_array_class`.

Test: m test-art-host-gtest
Test: testrunner.py --host --optimizing
Bug: 31113334
Change-Id: I191907c0053456bb57de425aa6ccd9668df818a2
diff --git a/dex2oat/linker/image_test.h b/dex2oat/linker/image_test.h
index 4b231ed..f0daf69 100644
--- a/dex2oat/linker/image_test.h
+++ b/dex2oat/linker/image_test.h
@@ -97,7 +97,7 @@
     return new std::unordered_set<std::string>(image_classes_);
   }
 
-  ArtMethod* FindCopiedMethod(ArtMethod* origin, mirror::Class* klass)
+  ArtMethod* FindCopiedMethod(ArtMethod* origin, ObjPtr<mirror::Class> klass)
       REQUIRES_SHARED(Locks::mutator_lock_) {
     PointerSize pointer_size = class_linker_->GetImagePointerSize();
     for (ArtMethod& m : klass->GetCopiedMethods(pointer_size)) {