t4040: remove test that succeeded for a wrong reason

"diff-tree -b --exit-code" without "--patch" exits with 0 status,
not because it finds that the two input files are equivalent while
ignoring whitespaces, but because the implied "--raw" mode always
exits with 0 when whitespace tweaking options like "-b" and "-w"
are given, which is a long-standing bug.

We are about to fix it so that "--raw" and friends report the
differences with the exit status (even though they ignore the
whitespace tweaking options when producing their output), which
will make this test, which succeeded for a wrong reason, start
failing.  Remove it.

Signed-off-by: Junio C Hamano <[email protected]>

Author: gitster

t/t4040-whitespace-status.sh

@@ -28,8 +28,7 @@ test_expect_success 'diff-tree --exit-code' '
 
 test_expect_success 'diff-tree -b --exit-code' '
 	git diff -b --exit-code HEAD^ HEAD &&
-	git diff-tree -b -p --exit-code HEAD^ HEAD &&
-	git diff-tree -b --exit-code HEAD^ HEAD
+	git diff-tree -b -p --exit-code HEAD^ HEAD
 '
 
 test_expect_success 'diff-index --cached --exit-code' '