patch 8.2.2426: allowing 'completefunc' to switch windows causes trouble

Problem:    Allowing 'completefunc' to switch windows causes trouble.
Solution:   use "textwinlock" instead of "textlock".
diff --git a/src/testdir/test_popup.vim b/src/testdir/test_popup.vim
index 9175ff1..2d0625b 100644
--- a/src/testdir/test_popup.vim
+++ b/src/testdir/test_popup.vim
@@ -342,7 +342,7 @@
   setlocal completefunc=DummyCompleteOne
   call setline(1, 'one')
   /^one
-  call assert_fails('call feedkeys("A\<C-X>\<C-U>\<C-N>\<Esc>", "x")', 'E578:')
+  call assert_fails('call feedkeys("A\<C-X>\<C-U>\<C-N>\<Esc>", "x")', 'E565:')
   call assert_equal(winid, win_getid())
   call assert_equal('onedef', getline(1))
   q!
@@ -642,8 +642,8 @@
   set completefunc=MessComplete
   new
   call setline(1, 'Ju')
-  call feedkeys("A\<c-x>\<c-u>/\<esc>", 'tx')
-  call assert_equal('Oct/Oct', getline(1))
+  call assert_fails('call feedkeys("A\<c-x>\<c-u>/\<esc>", "tx")', 'E578:')
+  call assert_equal('Jan/', getline(1))
   bwipe!
   set completefunc=
 endfunc