input: Write a python function to delete every third character from a string.
  assert delete_third_characters("abcdefghij") == "abdeghj"
  assert delete_third_characters("1234567890") == "1245780"
  assert delete_third_characters("HelloWorld!") == "HeWorld!"
output: def delete_third_characters(s: str) -> str:
      return ''.join(char for i, char in enumerate(s) if (i + 1) % 3 != 0)