Test 8 in t5407 appears to be an accidental exact duplicate of of test 5;
the testcode is identical and has identical repo state, but the test
description is different and suggests that rebase -m followed by rebase
--skip was what was actually supposed to be tested. Modify the test to
include the -m option.
Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>