Fix typo

app/controllers/api/v1/activities_controller.rb

 
   def update
     if @activity.update(activity_params)
-      render json: @product
+      render json: @activity
     else
-      render json: @product.erros, status: :unprocessable_entity
+      render json: @activity.errors, status: :unprocessable_entity
     end
   end