input: Write a python function to remove specific characters from a string.
  assert remove_specific_chars("ABCDEFGHIJKLMNOPQRSTUVWXYZ", ['A', 'C', 'D', 'E']) == "BFGHIJKLMNOPQRSTUVWXYZ"
  assert remove_specific_chars("HELLO WORLD", ['L', 'O']) == "HE WRD"
  assert remove_specific_chars("PYTHON PROGRAMMING", ['P', 'G', 'N']) == "YTHON RORAMMI"
output: def remove_specific_chars(s, chars):
      return ''.join(c for c in s if c not in chars)