patch 8.1.1806: test for display updating doesn't check without statusline

Problem:    Test for display updating doesn't check without statusline.
Solution:   Add screenshots without a status line.
diff --git a/src/testdir/test_display.vim b/src/testdir/test_display.vim
index dfa641b..6856759 100644
--- a/src/testdir/test_display.vim
+++ b/src/testdir/test_display.vim
@@ -88,6 +88,17 @@
   call term_sendkeys(buf, ":4put\<cr>")
   call VerifyScreenDump(buf, 'Test_scroll_no_region_3', {})
 
+  call term_sendkeys(buf, ":undo\<cr>")
+  call term_sendkeys(buf, ":undo\<cr>")
+  call term_sendkeys(buf, ":set laststatus=0\<cr>")
+  call VerifyScreenDump(buf, 'Test_scroll_no_region_4', {})
+
+  call term_sendkeys(buf, ":3delete\<cr>")
+  call VerifyScreenDump(buf, 'Test_scroll_no_region_5', {})
+
+  call term_sendkeys(buf, ":4put\<cr>")
+  call VerifyScreenDump(buf, 'Test_scroll_no_region_6', {})
+
   " clean up
   call StopVimInTerminal(buf)
   call delete('Xtestscroll')