patch 8.1.2069: test for SafeStateAgain may still fail

Problem:    Test for SafeStateAgain may still fail.
Solution:   Send another message to trigger SafeStateAgain.
diff --git a/src/testdir/test_autocmd.vim b/src/testdir/test_autocmd.vim
index 1f901a9..f2c9af5 100644
--- a/src/testdir/test_autocmd.vim
+++ b/src/testdir/test_autocmd.vim
@@ -2250,7 +2250,9 @@
   call WaitForAssert({-> assert_match('^xxxx', term_getline(buf, 6))}, 1000)
 
   call term_sendkeys(buf, ":let g:again = ''\<CR>:call CallTimer()\<CR>")
-  call term_wait(buf, 50)
+  call term_wait(buf)
+  call term_sendkeys(buf, ":\<CR>")
+  call term_wait(buf)
   call term_sendkeys(buf, ":echo g:again\<CR>")
   call WaitForAssert({-> assert_match('xtx', term_getline(buf, 6))}, 1000)