patch 8.2.2285: Vim9: cannot set an option to a false

Problem:    Vim9: cannot set an option to a false.
Solution:   For VAR_BOOL use string "0". (closes #7603)
diff --git a/src/testdir/test_vim9_builtin.vim b/src/testdir/test_vim9_builtin.vim
index 74031d4..4eb2d76 100644
--- a/src/testdir/test_vim9_builtin.vim
+++ b/src/testdir/test_vim9_builtin.vim
@@ -662,6 +662,8 @@
   settabwinvar(1, 1, '&ts', 15)
   &ts->assert_equal(15)
   setlocal ts=8
+  settabwinvar(1, 1, '&list', false)
+  &list->assert_equal(false)
   settabwinvar(1, 1, '&list', true)
   &list->assert_equal(true)
   setlocal list&