input: Write a python function to replace numbers greater than 5 in a list with 0.
  assert replace_numbers([1, 4, 7, 9, 6, 8]) == [1, 4, 0, 0, 0, 0]
  assert replace_numbers([10, 5, 3, 12, 2, 8]) == [0, 5, 3, 0, 2, 0]
  assert replace_numbers([1, 2, 3, 4, 5]) == [1, 2, 3, 4, 5]
output: def replace_numbers(lst):
      return [x if x <= 5 else 0 for x in lst]