t6036: remove pointless test that expects failure

t6036: remove pointless test that expects failure

One test in t6036 prepares a file whose contents contain these
lines:

	<<<<<<< Temporary merge branch 1
	C
	=======
	B
	>>>>>>> Temporary merge branch 2

and uses recursive merge strategy to run criss-cross merge with it.

Manual merge resolution by users fundamentally depends on being able
to distinguish the tracked contents from the separator lines added
by "git merge" in order to allow users to tell which block of lines
came from where.  You can deliberately craft a file with lines that
resemble conflict marker lines to make it impossible for the user
(the outer merge of merge-recursive counts as a user of the result
of "virtual parent" merge) to tell which part is which, and write a
test to demonstrate that with such a file that "git merge" cannot
fundamentally work well and has to fail.

It however is pointless and waste of time and resource to run such a
test that asserts the obvious.

In real life, people who do need to track files with such lines that
have <<<< ==== >>>> as their prefixes set the conflict-marker-size
attribute to make sure they will be able to tell between the tracked
lines that happen to begin with these (confusing) prefixes and the
marker lines that are added by "git merge".

Remove the test as pointless waste of resource.

Signed-off-by: Junio C Hamano <gitster@pobox.com>