erp5/tests: Replace readfp by read_file
Python 3.12 removes ConfigParser.readfp, see https://github.com/python/cpython/blob/dd0e8a62df8be2a09ef6035b4c92bd9a68a7b918/Lib/configparser.py#L757-L764
Edited by Boxiang Sun
Python 3.12 removes ConfigParser.readfp, see https://github.com/python/cpython/blob/dd0e8a62df8be2a09ef6035b4c92bd9a68a7b918/Lib/configparser.py#L757-L764