t3404-rebase-interactive.sh: fix typos in title of a rewording test

t3404-rebase-interactive.sh: fix typos in title of a rewording test

This test was introduced by commit 0c164ae7a ("rebase -i: add another
reword test", 2021-08-20). I didn't quite get what it was meant to do,
so here's an explanation from Phillip:

The purpose of the test is to ensure that

  (i) There are no uncommitted changes when the editor runs. i.e., we
      commit without running the editor and then reword by amending
      that commit. This ensures that we have the same user experience
      whether or not the commit was fast-forwarded [1].

 (ii) That the todo list is re-read after the commit has been reworded.
      This is to allow the user to update the todo list while the rebase
      is paused for editing the commit message.

[1] https://lore.kernel.org/git/20190812175046.GM20404@szeder.dev/

Signed-off-by: Oswald Buddenhagen <oswald.buddenhagen@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>