LibCore: Remove deferred_invoke overload with Object& parameter

This is not necessary because the user can just use this, which is
referenced until the deferred invocation is complete.

Userland/Libraries/LibCore/Object.cpp

@@ -162,11 +162,6 @@ void Object::dump_tree(int indent)
     });
 }
 
-void Object::deferred_invoke(Function<void(Object&)> invokee)
-{
-    deferred_invoke([invokee = move(invokee), this] { invokee(*this); });
-}
-
 void Object::deferred_invoke(Function<void()> invokee)
 {
     Core::deferred_invoke([invokee = move(invokee), strong_this = NonnullRefPtr(*this)] { invokee(); });

Userland/Libraries/LibCore/Object.h

@@ -129,7 +129,6 @@ public:
 
     void dump_tree(int indent = 0);
 
-    void deferred_invoke(Function<void(Object&)>);
     void deferred_invoke(Function<void()>);
 
     void save_to(JsonObject&);