Issue #21396: Fix TextIOWrapper(..., write_through=True) to not force a flush() on...

Patch by akira.

diff --cc Lib/test/test_io.py
Simple merge

diff --cc Misc/NEWS
index 22dfc1055245b5085966336cd1d8b70f3b619289,29634fcf407ff1883b558fb9e9eb6abb91722c32..6fc0a13dc6ee64efddca36eb21aafa445cad761a
--- 1/Misc/NEWS
--- 2/Misc/NEWS
+++ b/Misc/NEWS
@@@ -69,8 -56,6 +69,11 @@@ Core and Builtin
  Library
  -------
  
++- Issue #21396: Fix TextIOWrapper(..., write_through=True) to not force a
++  flush() on the underlying binary stream.  Patch by akira.
++
 +- Issue #18314: Unlink now removes junctions on Windows. Patch by Kim Gräsman
 +
  - Issue #21088: Bugfix for curses.window.addch() regression in 3.4.0.
    In porting to Argument Clinic, the first two arguments were reversed.
  

diff --cc Modules/_io/textio.c
Simple merge