patch 8.2.2420: too many problems with using all autocommand events

Problem:    Too many problems with using all autocommand events.
Solution:   Disallow defining an autocommand for all events.
diff --git a/src/testdir/test_window_cmd.vim b/src/testdir/test_window_cmd.vim
index f26b447..07347a3 100644
--- a/src/testdir/test_window_cmd.vim
+++ b/src/testdir/test_window_cmd.vim
@@ -567,8 +567,8 @@
 
 func Test_access_freed_mem()
   call assert_equal(&columns, winwidth(0))
-  " This was accessing freed memory
-  au * 0 vs xxx
+  " This was accessing freed memory (but with what events?)
+  au BufEnter,BufLeave,WinEnter,WinLeave 0 vs xxx
   arg 0
   argadd
   call assert_fails("all", "E242:")