SAK-23029 fix regression so that last maintainer isn't able to be removed from site


git-svn-id: https://source.sakaiproject.org/svn/site-manage/trunk@123190 66ffb92e-73f9-0310-93c1-f5514f145a0a
SAK-23029 update maintainer deletion alert message


git-svn-id: https://source.sakaiproject.org/svn/site-manage/trunk@123191 66ffb92e-73f9-0310-93c1-f5514f145a0a