ART: Clean up checks in CheckProxyMethod().

The non-proxy method, `np`, is always the same as the
`prototype`, so it's not really worth comparing their
members. That's been the case since
    https://android-review.googlesource.com/148090 .

We've see the comparison of the return type hit a CHECK()
failure for ObjPtr<> cookie. This can happen since
    https://android-review.googlesource.com/431679
if the return type is evicted from the DexCache and we go
through the slow path.

Test: m test-art-host-gtest
Test: testrunner.py --host
Bug: 30627598
Change-Id: I11f9ea86326be6ef9043ac5f170d74165ac11343
diff --git a/runtime/class_linker.cc b/runtime/class_linker.cc
index 1beb783..93b6dd1 100644
--- a/runtime/class_linker.cc
+++ b/runtime/class_linker.cc
@@ -4692,14 +4692,8 @@
 
   // The proxy method doesn't have its own dex cache or dex file and so it steals those of its
   // interface prototype. The exception to this are Constructors and the Class of the Proxy itself.
-  auto* np = method->GetInterfaceMethodIfProxy(image_pointer_size_);
-  CHECK_EQ(prototype->GetDeclaringClass()->GetDexCache(), np->GetDexCache());
   CHECK_EQ(prototype->GetDexMethodIndex(), method->GetDexMethodIndex());
-
-  CHECK_STREQ(np->GetName(), prototype->GetName());
-  CHECK_STREQ(np->GetShorty(), prototype->GetShorty());
-  // More complex sanity - via dex cache
-  CHECK_EQ(np->ResolveReturnType(), prototype->ResolveReturnType());
+  CHECK_EQ(prototype, method->GetInterfaceMethodIfProxy(image_pointer_size_));
 }
 
 bool ClassLinker::CanWeInitializeClass(ObjPtr<mirror::Class> klass, bool can_init_statics,