doc: Pickle with protocol=0 in python 3 does not produce a 'human-readable' format

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-09-20.22:53:12.087>
labels = ['type-bug', '3.8', '3.9', '3.10', 'docs']
title = "doc: Pickle with protocol=0 in python 3 does not produce a 'human-readable' format"
updated_at = <Date 2021-03-25.23:18:24.098>
user = 'https://github.com/aggieNick02'

bugs.python.org fields:

activity = <Date 2021-03-25.23:18:24.098>
actor = 'iritkatriel'
assignee = 'docs@python'
closed = False
closed_date = None
closer = None
components = ['Documentation']
creation = <Date 2019-09-20.22:53:12.087>
creator = 'aggieNick02'
dependencies = []
files = []
hgrepos = []
issue_num = 38241
keywords = []
message_count = 6.0
messages = ['352907', '352919', '352920', '352958', '353004', '353014']
nosy_count = 4.0
nosy_names = ['docs@python', 'serhiy.storchaka', 'josh.r', 'aggieNick02']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue38241'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']