TextIOWrapper usage of IncrementalEncoder doesn't match documentation around `final=`

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-10-15.14:22:34.158>
labels = ['3.8', 'type-bug', '3.7', '3.9', 'expert-IO']
title = 'BUG Modules/_io/texio.c'
updated_at = <Date 2019-10-15.15:42:43.658>
user = 'https://github.com/jamercee'

bugs.python.org fields:

activity = <Date 2019-10-15.15:42:43.658>
actor = 'serhiy.storchaka'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['IO']
creation = <Date 2019-10-15.14:22:34.158>
creator = 'jamercee'
dependencies = []
files = []
hgrepos = []
issue_num = 38485
keywords = []
message_count = 1.0
messages = ['354733']
nosy_count = 3.0
nosy_names = ['benjamin.peterson', 'stutzbach', 'jamercee']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue38485'
versions = ['Python 2.7', 'Python 3.7', 'Python 3.8', 'Python 3.9']