patch 8.1.1440: win_execute() test fails

Problem:    Win_execute() test fails.
Solution:   Adjust the expected error number.  Move to popup test.
diff --git a/src/testdir/test_popupwin.vim b/src/testdir/test_popupwin.vim
index 7c3cd94..1c8f7ef 100644
--- a/src/testdir/test_popupwin.vim
+++ b/src/testdir/test_popupwin.vim
@@ -118,6 +118,7 @@
   call assert_fails('call win_execute(winid, "vsplit")', 'E994:')
   call assert_fails('call win_execute(winid, "close")', 'E994:')
   call assert_fails('call win_execute(winid, "bdelete")', 'E994:')
+  call assert_fails('call win_execute(winid, "bwipe!")', 'E994:')
   call assert_fails('call win_execute(winid, "tabnew")', 'E994:')
   call assert_fails('call win_execute(winid, "tabnext")', 'E994:')
   call assert_fails('call win_execute(winid, "next")', 'E994:')