input: Write a function to remove all occurrences of the given element in a given array. If the given array is empty then return an empty array.
  assert remove_element([2, 4, 5, 7, 4, 2], 4) == [2, 5, 7, 2]
  assert remove_element([2, 4, 5, 7, 4, 2], 2) == [4, 5, 7, 4]
  assert remove_element([4, 4, 4, 4], 4) == []
  assert remove_element([], 4) == []
  assert remove_element([3, 5, 3, 1, 2], 6) == [3, 5, 3, 1, 2]
output: def remove_element(arr, elem):
      return [x for x in arr if x != elem]