t6023-merge-file.sh: fix and mark as broken invalid tests

t6023-merge-file.sh: fix and mark as broken invalid tests

Tests "merge without conflict (missing LF at EOF" and "merge result
added missing LF" are meaningless - the first one is identical to
"merge without conflict" and the second compares results of those
identical tests, which are always same.

This has been so since their addition in ba1f5f3537. Probably "new4.txt"
was meant to be used instead of "new2.txt". Unfortunately, the current
merge-file breaks with new4 - conflict is reported. They also fail at
that revision if fixed.

Fix the file reference to "new4.txt" and mark the tests as failing -
they look like legitimate expectations, just not satisfied at time
being.

Signed-off-by: Max Kirillov <max@max630.net>
Acked-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>