patch 8.2.2296: cannot use CTRL-N and CTRL-P in a popup menu

Problem:    Cannot use CTRL-N and CTRL-P in a popup menu.
Solution:   Use CTRL-N like <Down> and CTRL-P like <Up>. (closes #7614)
diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index bfc0494..7335c1c 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -3797,4 +3797,10 @@
   endtry
 endfunc
 
+func Test_popup_filter_menu()
+  let colors = ['red', 'green', 'blue']
+  call popup_menu(colors, #{callback: {_, result -> assert_equal('green', colors[result - 1])}})
+  call feedkeys("\<c-n>\<c-n>\<c-p>\<cr>", 'xt')
+endfunc
+
 " vim: shiftwidth=2 sts=2