Rename ObjPtr::Decode to ObjPtr::Ptr

Done to prevent ambiguity with ScopedObjectAccess::Decode.

Bug: 31113334

Test: test-art-host
Change-Id: I07a2497cc9cf66386311798933547471987fc316
diff --git a/runtime/class_linker_test.cc b/runtime/class_linker_test.cc
index 4a926e7..5466539 100644
--- a/runtime/class_linker_test.cc
+++ b/runtime/class_linker_test.cc
@@ -875,7 +875,7 @@
   uint32_t type_idx = klass->GetClassDef()->class_idx_;
   ObjPtr<mirror::DexCache> dex_cache = klass->GetDexCache();
   const DexFile& dex_file = klass->GetDexFile();
-  EXPECT_EQ(dex_cache->GetResolvedType(type_idx), klass.Decode());
+  EXPECT_EQ(dex_cache->GetResolvedType(type_idx), klass.Ptr());
   EXPECT_OBJ_PTR_EQ(
       class_linker_->LookupResolvedType(dex_file, type_idx, dex_cache, class_loader.Get()),
       klass);