Update icons for macOS 11

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-11-17.11:37:00.773>
labels = ['OS-mac', 'type-feature', '3.8', '3.9', '3.10']
title = 'Update icons for macOS 11'
updated_at = <Date 2020-11-17.15:35:34.589>
user = 'https://github.com/Forrest-J'

bugs.python.org fields:

activity = <Date 2020-11-17.15:35:34.589>
actor = '17jiangz1'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['macOS']
creation = <Date 2020-11-17.11:37:00.773>
creator = '17jiangz1'
dependencies = []
files = []
hgrepos = []
issue_num = 42386
keywords = ['patch']
message_count = 4.0
messages = ['381224', '381237', '381241', '381250']
nosy_count = 4.0
nosy_names = ['ronaldoussoren', 'ned.deily', 'python-dev', '17jiangz1']
pr_nums = ['23339']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue42386'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']