[3.13] gh-98552: Revert (unneeded, already done elsewhere) "flush std streams in the multiprocessing forkserver before fork (GH-141849)" (GH-141871) (#141873)

gh-98552: Revert (unneeded, already done elsewhere) "flush std streams in the multiprocessing forkserver before fork (GH-141849)" (GH-141871)

Revert (unneeded, already done elsewhere) "gh-98552: flush std streams in the multiprocessing forkserver before fork (GH-141849)"

This reverts commit 58badb1.
(cherry picked from commit 614a28b)

Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com>

Author: miss-islington

Lib/multiprocessing/forkserver.py

@@ -270,7 +270,6 @@ def sigchld_handler(*_unused):
                                     len(fds)))
                         child_r, child_w, *fds = fds
                         s.close()
-                        util._flush_std_streams()
                         pid = os.fork()
                         if pid == 0:
                             # Child