Update mailing list URL's

Author: nickygerritsen

website/about.shtml

@@ -76,7 +76,7 @@ you the freedom to use it for any purpose, without cost, make changes
 that you require and share those with the community.</p>
 
 <p>You can reach us through the development mailinglist
-<a href="https://www.domjudge.org/mailman/listinfo/domjudge-devel">DOMjudge-devel</a>.
+<a href="https://www.domjudge.org/mailman/postorius/lists/domjudge-devel.domjudge.org/">DOMjudge-devel</a>.
 (You need to be subscribed to the list before you can post, to counter spam.)
 This is also the place to get help with your questions about installing
 or using DOMjudge.</p>

website/development.shtml

@@ -22,13 +22,13 @@ for how to run DOMjudge from git sources.</p>
 <a href="https://github.com/DOMjudge/domjudge/issues">our Github project</a>.
 You may report a new issue there.
 If you have a <em>question</em> or you are unsure whether what you're seeing is
-a bug, please discuss it on <a href="https://www.domjudge.org/mailman/listinfo/domjudge-devel">the development mailinglist</a> or
+a bug, please discuss it on <a href="https://www.domjudge.org/mailman/postorius/lists/domjudge-devel.domjudge.org/">the development mailinglist</a> or
 chat beforehand (see below).</p>
 
 <h2>Mailinglist and chat</h2>
 
 <p>You are welcome to subscribe to our
-<a href="https://www.domjudge.org/mailman/listinfo/domjudge-devel">development mailinglist</a>
+<a href="https://www.domjudge.org/mailman/postorius/lists/domjudge-devel.domjudge.org/">development mailinglist</a>
 for discussions on development, but also for asking general
 questions on using and installing DOMjudge (you need to subscribe
 to the list before you can post).

website/download.shtml

@@ -35,7 +35,7 @@ dated <!--#echo var="dj_rc_branch_date" -->.</p>
 </div></div>
 
 <p>To get notifications of new releases, subscribe to the low volume
-<a href="https://www.domjudge.org/mailman/listinfo/domjudge-announce">announcements
+<a href="https://www.domjudge.org/mailman/postorius/lists/domjudge-announce.domjudge.org/">announcements
 mailing list</a>.</p>
 
 <h3>DOMjudge docker images</h3>