Unnecessary python2->3 code can likely be removed

[alexrudd2]

Since Python2 has been dropped, I think this code can be dropped and its callers changed to use encode() directly.

pymodbus/pymodbus/utilities.py

Lines 156 to 164 in 9c6acc3

	def make_byte_string(byte_string):
	"""Return byte string from a given string, python3 specific fix.
	:param byte_string:
	:return:
	"""
	if isinstance(byte_string, str):
	byte_string = byte_string.encode()
	return byte_string