fix child on_attach

src/application/application.hpp

@@ -28,11 +28,6 @@ namespace VE
       void push_layer(Args*... args) 
       { 
         (m_layers_stack.push_back(args), ...); 
-      }
-
-      template<typename... Args>
-      void on_attach(Args*... args) 
-      { 
         (args->on_attach(), ...);
       }