Change "DELETE" to "CANCEL" for waitlist

In order to have consistency and reduce confusion for admin and sub admin, please change the X column for a waitlist to say CANCEL (just like it says for registration). Also, the hover text should say CANCEL as well.  It doesn't make sense to have people deleted from the waitlist and canceled from the registration list.  The result is the same. We are canceling their spot on the waitlist.