merge-ort: remove code obsoleted by other changes

merge-ort: remove code obsoleted by other changes

Commit 66b209b86a ("merge-ort: implement CE_SKIP_WORKTREE handling with
conflicted entries", 2021-03-20) added some code for merge-ort to handle
conflicted and skip_worktree entries in general.  Included in this was
an ugly hack for dealing with present-despite-skipped entries and a
testcase (t6428.2) specific to that hack, since at that time users could
accidentally get files into that state when using a sparse checkout.

However, with the merging of 82386b4496 ("Merge branch
'en/present-despite-skipped'", 2022-03-09), that class of problems was
addressed globally and in a much cleaner way.  As such, the
present-despite-skipped hack in merge-ort is no longer needed and can
simply be removed.

No additional testcase is needed here; t6428.2 was written to test the
necessary functionality and is being kept.  The fact that this test
continues to pass despite the code being removed shows that the extra
code is no longer necessary.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>