texinfo: remove unneeded sed

It works out of box with glibc-2.35.  I think this issue is already
fixed at glibc side, by the commit:

commit 0b5ca7c3e551e5502f3be3b06453324fe8604e82
Author: Paul Eggert <eggert@cs.ucla.edu>
Date:   Tue Sep 21 07:47:45 2021 -0700

    regex: copy back from Gnulib

    Copy regex-related files back from Gnulib, to fix a problem with
    static checking of regex calls noted by Martin Sebor.  This merges the
    following changes:

    * New macro __attribute_nonnull__ in misc/sys/cdefs.h, for use later
    when copying other files back from Gnulib.

    ... ... (unrelated things trimmed)

0 files changed, 0 insertions, 0 deletions