argparse: auto-generated synopsis omits REMAINDER argument

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-09-24.23:40:02.028>
labels = ['3.8', 'library']
title = 'argparse: auto-generated synopsis omits REMAINDER argument'
updated_at = <Date 2020-09-24.23:42:31.094>
user = 'https://bugs.python.org/rrt'

bugs.python.org fields:

activity = <Date 2020-09-24.23:42:31.094>
actor = 'rrt'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2020-09-24.23:40:02.028>
creator = 'rrt'
dependencies = []
files = []
hgrepos = []
issue_num = 41856
keywords = []
message_count = 2.0
messages = ['377469', '377470']
nosy_count = 1.0
nosy_names = ['rrt']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue41856'
versions = ['Python 3.8']