Remove BBQ, Beer, Silver and Gold as available sponsor slots

Former-commit-id: f66aeb1

content/events/2016-amsterdam/sponsor.md

@@ -82,11 +82,11 @@ Here is a quick overview of the options for this year:
 <table class="tg">
   <tr>
     <th class="tg-yw4l"></th>
-    <th class="tg-4bw1">Bronze<br>(6 slots)</th>
-    <th class="tg-4bw1">Silver<br>(4 slots)</th>
-    <th class="tg-4bw1">Gold<br>(8 slots)</th>
-    <th class="tg-4bw1">Beer<br>(1 slot)</th>
-    <th class="tg-4bw1">BBQ<br>(1 slot)</th>
+    <th class="tg-4bw1">Bronze<br></th>
+    <th class="tg-4bw1"><s>Silver</s><br><b>SOLD OUT</b></th>
+    <th class="tg-4bw1"><s>Gold</s><br><b>SOLD OUT</b></th>
+    <th class="tg-4bw1"><s>Beer</s><br><b>SOLD OUT</b></th>
+    <th class="tg-4bw1"><s>BBQ</s><br><b>SOLD OUT</b></th>
   </tr>
   <tr>
     <td class="tg-yw4l"></td>