vim-patch:8.1.0815: dialog for file changed outside of Vim not tested (#28184)

Problem:    Dialog for file changed outside of Vim not tested.
Solution:   Add a test.  Move FileChangedShell test.  Add 'L' flag to
            feedkeys().

5e66b42aae

Co-authored-by: Bram Moolenaar <Bram@vim.org>

test/old/testdir/test_functions.vim

@@ -2590,8 +2590,6 @@ endfunc
 
 " Test confirm({msg} [, {choices} [, {default} [, {type}]]])
 func Test_confirm()
-  " requires a UI to be active
-  throw 'Skipped: use test/functional/vimscript/input_spec.lua'
   CheckUnix
   CheckNotGui