git-rebase.sh: fix typo in an error message
git-rebase.sh: fix typo in an error message

Fix a typo in the error messages which is shown if it seems that a
rebase is already in progress.

Signed-off-by: Ralf Thielow <d790fea1760bfa57e221e3da971e544c5c4e0598@gmail.com>
Signed-off-by: Junio C Hamano <a6723cc3f76163bf7adb636a73ac3b0ceb3e6b9b@pobox.com>

destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git,destenson/git