docs/website: fix </div> soup

Commit bdcdc4428c4a64582daba9370d9eac92e2799e55 got the div soup
wrong, adjust this.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>

docs/website/sponsors.html

@@ -73,7 +73,6 @@
 	    </div>
 	  </div>
 	</div>
-      </div>
 
     </div>
     </div>