[webui] don't confuse a user with "maintenance" project

The check box is only confusing the user in first place.
It is not a project for preparing a maintenance update (but for creating
a new maintenance team coordination place). This is so rarly used
that it harms more then it helps here.
(if we re-implement, we should do it via a selection box for all the
 other (and more often used) types)

src/api/app/views/webui/project/_form.html.erb

@@ -24,7 +24,6 @@
       <% end %>
       <%= check_box_tag :disable_publishing, false %>Disable build results publishing.
       <br/>
-      <%= check_box_tag :maintenance_project, false %>Create as maintenance project.
     </p>
     <p><%= submit_tag "Create Project" %></p>
 <% end %>