LibJS: Make Cell::initialize() return void

Stop worrying about tiny OOMs.

Work towards #20405

Userland/Libraries/LibJS/Runtime/Object.cpp

@@ -74,9 +74,8 @@ Object::~Object()
         s_intrinsics.remove(this);
 }
 
-ThrowCompletionOr<void> Object::initialize(Realm&)
+void Object::initialize(Realm&)
 {
-    return {};
 }
 
 // 7.2 Testing and Comparison Operations, https://tc39.es/ecma262/#sec-testing-and-comparison-operations