Issue 03: Correct typo: psuedo vs pseudo in Spam.pm

Part 2/2 - rewrite of pull request https://github.com/bdraco/addon_securityadvisor/pull/3 - fix typo in Spam.pm. If this change + the changes in https://github.com/bdraco/addon_securityadvisor/pull/52 are committed, issue #3 can be closed.