input: Write a python function to remove numbers greater than a given number from a list.
  assert removeGreaterNum([1, 5, 6, 8, 9, 10], 7) == [1, 5, 6]
  assert removeGreaterNum([12, 3, 45, 7, 8], 10) == [3, 7, 8]
  assert removeGreaterNum([20, 15, 10, 5, 0], 15) == [10, 5, 0]
output: def removeGreaterNum(lst, num):
      return [x for x in lst if x <= num]