Since commit 8fe9c3f21dff (Merge branch 'en/rebase-merge-on-sequencer',
2019-02-06), --merge now uses the interactive backend (and matches its
behavior) so there is no separate merge backend anymore. Fix an
oversight in the docs that should have been updated with the previous
change.
Signed-off-by: Elijah Newren <newren@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>