Revert "Adds link to Robinhood"

This reverts commit e74f3d1a2358d8ee7aac69731e9a160a1bcf65f4.

docs/.templates/sidebarintro.html

@@ -14,7 +14,5 @@
 
 <div id="sponsors">
     <b>Sponsored by:</b>
-    <a href="https://robinhood.com">
-        <img src="https://s3-us-west-1.amazonaws.com/celerydocs/images/robinhood_logotype_green_left.png" />
-    </a>
+    <img src="https://s3-us-west-1.amazonaws.com/celerydocs/images/robinhood_logotype_green_left.png" />
 </div>

docs/.templates/sidebarlogo.html

@@ -14,7 +14,5 @@
 
 <div id="sponsors">
     <b>Sponsored by:</b>
-    <a href="https://robinhood.com">
-        <img src="https://s3-us-west-1.amazonaws.com/celerydocs/images/robinhood_logotype_green_left.png" />
-    </a>
+    <img src="https://s3-us-west-1.amazonaws.com/celerydocs/images/robinhood_logotype_green_left.png" />
 </div>