Merge branch 'pw/rebase-i-cleanup-fix' into maint-2.51

"git rebase -i" failed to clean-up the commit log message when the
command commits the final one in a chain of "fixup" commands, which
has been corrected.

* pw/rebase-i-cleanup-fix:
  sequencer: remove VERBATIM_MSG flag
  rebase -i: respect commit.cleanup when picking fixups

diff --cc sequencer.c
Simple merge

diff --cc t/t3415-rebase-autosquash.sh
Simple merge