add note about what to do if 'learner_expire_old_training', 'learner_sync' are irrelevant

git-svn-id: https://svn.apache.org/repos/asf/spamassassin/branches/bug-5293-pluginized-bayes@602913 13f79535-47bb-0310-9956-ffa450edef68
1 file changed