Remove address as per request

See also 53367a613b.

manufacturers.html

@@ -77,8 +77,7 @@
       may help to write backends for a variety of devices. Also tell us if any of the information in
       our lists is missing or wrong. So please contact the <a href="mailing-lists.html">sane-devel
       mailing list</a> with your information and ideas. If you don't want to subscribe to this list,
-      please write to Henning Meier-Geinitz (<a
-      href="mailto:henning@meier-geinitz.de">henning@meier-geinitz.de</a>).
+      please <a href="https://gitlab.com/sane-project/backends/issues">submit an issue</a>).
     </p>
 
     <hr>