patch 9.0.0650: some tests are failing

Problem:    Some tests are failing.
Solution:   Adjust for "<<<" showing up.
diff --git a/src/testdir/test_number.vim b/src/testdir/test_number.vim
index e854576..81f8f73 100644
--- a/src/testdir/test_number.vim
+++ b/src/testdir/test_number.vim
@@ -138,7 +138,7 @@
   call s:validate_cursor()
   let lines = s:screen_lines(1, 3)
   let expect = [
-\ "--1 aaaa",
+\ "<<< aaaa",
 \ "    aaaa",
 \ "    aaaa",
 \ ]