text: Title: Prevent handlers from cancelling
  Body: Perhaps I have gaps in understanding aiogram, but why can't I make handler cancellation protection?
  
  ```
  import asyncio
  import logging
  import os
  
  from aiogram import Bot, Dispatcher, types
  
  #API_TOKEN = os.getenv("BOT_TOKEN")
  API_TOKEN = "TOKEN"
  
  # Configure logging
  logging.basicConfig(level=logging.INFO)
  
  # Initialize bot and dispatcher
  bot = Bot(token=API_TOKEN)
  dp = Dispatcher(bot)
  
  def shielded(fn):
      async def wrapped(*args, **kwargs):
          await asyncio.shield(fn(*args, **kwargs))
  
      return wrapped
  
  
  @dp.message_handler()
  @shielded
  async def echo(message: types.Message, *args, **kwargs):
      try:
          await asyncio.sleep(7)
          await message.answer(message.text)
      except asyncio.CancelledError:
          print("handler cancelled :(")
  
  async def cancel_dp_with_delay(dp, sec):
      await asyncio.sleep(sec)
      dp.stop_polling()
      
  
  
  async def main():
      asyncio.create_task(cancel_dp_with_delay(dp, 5))
      await dp.start_polling()
      await dp.wait_closed()
      await asyncio.sleep(3)
  
  if __name__ == '__main__':
      asyncio.run(main())
  ```
      