docs/website: correct association e-mail address

It is buildroot-association@buildroot.org, not @lists.buildroot.org.

Reported-by: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

docs/website/association.html

@@ -109,7 +109,7 @@
 	  receipt.</p>
 
 	  <p>Please
-	  contact <a href="mailto:buildroot-association@lists.buildroot.org">buildroot-association@lists.buildroot.org</a>
+	  contact <a href="mailto:buildroot-association@buildroot.org">buildroot-association@buildroot.org</a>
 	  if you are a company interested in making a donation.</p>
 
 	</div>