Swapped out placeholder text on teams admin page

Changed "simple Teams description" placeholder subtitle to "allow you
to organize groups of people that have a common focus. Use teams to
simplify the process of assigning roles to groups of people."

app/views/admin/teams/index.html.haml

 %h3.page_title
   Teams
   %small
-    simple Teams description
+    allow you to organize groups of people that have a common focus. Use teams to simplify the process of assigning roles to groups of people.
 
   = link_to 'New Team', new_admin_team_path, class: "btn btn-small pull-right"
   %br