Make invitation table heading clearer

app/views/offerers/show/_employees.html.erb

@@ -61,7 +61,7 @@
       <% if invitations.any? %>
         <table class="table table-condensed">
           <thead>
-            <th>E-mail</th>
+            <th>Pending Invitations</th>
             <th></th>
           </thead>
           <tbody>