OC 5310 Fix registration link

Was openclinica.com/designer-registration, Alicia pointed out that it should be openclinica.com/rule-designer-registration in:

https://jira.openclinica.com/browse/OC-5310?focusedCommentId=25153&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-25153