Update email body (html+text)

app/views/notify/issue_due_email.html.haml

@@ -7,7 +7,7 @@
     Assignee: #{@issue.assignee_list}
 
 %p
-  This Issue has a new due date: #{ @issue.due_date }
+  This issue is due on: #{ @issue.due_date }
 
 - if @issue.description
   %div

app/views/notify/issue_due_email.text.erb

-An Issue had its due date updated.
+The following issue is due on <%= @issue.due_date %>:
 
 Issue <%= @issue.iid %>: <%= url_for(project_issue_url(@issue.project, @issue)) %>
 Author:    <%= @issue.author_name %>
 Assignee:  <%= @issue.assignee_list %>
-New Due Date: <%= @issue.due_date %>
 
 <%= @issue.description %>