Normalize handling of negative timeouts in subprocess.py

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2022-02-18.17:26:30.966>
labels = ['3.8', 'library', '3.9', '3.10', '3.11']
title = 'Normalize handling of negative timeouts in subprocess.py'
updated_at = <Date 2022-02-18.17:47:08.845>
user = 'https://github.com/jkloth'

bugs.python.org fields:

activity = <Date 2022-02-18.17:47:08.845>
actor = 'jkloth'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2022-02-18.17:26:30.966>
creator = 'jkloth'
dependencies = []
files = []
hgrepos = []
issue_num = 46790
keywords = []
message_count = 2.0
messages = ['413496', '413497']
nosy_count = 3.0
nosy_names = ['vstinner', 'jkloth', 'eryksun']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue46790'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10', 'Python 3.11']