patch 8.1.2074: test for SafeState autocommand is a bit flaky

Problem:    Test for SafeState autocommand is a bit flaky.
Solution:   Add to list of flaky tests.
diff --git a/src/testdir/runtest.vim b/src/testdir/runtest.vim
index d9177e0..0d53a75 100644
--- a/src/testdir/runtest.vim
+++ b/src/testdir/runtest.vim
@@ -307,6 +307,7 @@
 
 " Names of flaky tests.
 let s:flaky_tests = [
+      \ 'Test_autocmd_SafeState()',
       \ 'Test_call()',
       \ 'Test_channel_handler()',
       \ 'Test_client_server()',