patch 8.2.4505: Vim9: outdated "autocmd nested" still works

Problem:    Vim9: outdated "autocmd nested" still works.
Solution:   Do not accept the :autocmd argument "nested" without "++" in Vim9
            script.
diff --git a/src/testdir/test_autocmd.vim b/src/testdir/test_autocmd.vim
index d3c9b89..7be0c18 100644
--- a/src/testdir/test_autocmd.vim
+++ b/src/testdir/test_autocmd.vim
Binary files differ