patch 9.0.1435: scrolling too many lines when 'wrap' and 'diff' are set

Problem:    Scrolling too many lines when 'wrap' and 'diff' are set.
Solution:   Only scroll by screenlines for 'diff' when 'wrap' is not set.
            (closes #12211)
diff --git a/src/testdir/test_diffmode.vim b/src/testdir/test_diffmode.vim
index d9ffbb3..d60de50 100644
--- a/src/testdir/test_diffmode.vim
+++ b/src/testdir/test_diffmode.vim
Binary files differ