patch 8.2.3626: "au! event" cannot be followed by another command

Problem:    "au!" and "au! event" cannot be followed by another command as
            documented.
Solution:   When a bar is found set nextcmd.
diff --git a/src/testdir/test_autocmd.vim b/src/testdir/test_autocmd.vim
index 045320e..4bdb8dc 100644
--- a/src/testdir/test_autocmd.vim
+++ b/src/testdir/test_autocmd.vim
Binary files differ