Update management UI footer links for the new website

and drop a link to Slack, which has too many limitations
in its free version at our scale. Discord is the primary
option now.

(cherry picked from commit 7b9f2ca)

Author: michaelklishin

deps/rabbitmq_management/priv/www/js/tmpl/layout.ejs

@@ -44,15 +44,14 @@
 <div id="footer">
   <ul>
     <li><a rel="noopener noreferrer" href="api/" target="_blank">HTTP API</a></li>
-    <li><a rel="noopener noreferrer" href="https://www.rabbitmq.com/documentation.html" target="_blank">Documentation</a></li>
-    <li><a rel="noopener noreferrer" href="https://www.rabbitmq.com/getstarted.html" target="_blank">Tutorials</a></li>
-    <li><a rel="noopener noreferrer" href="https://www.rabbitmq.com/changelog.html" target="_blank">New releases</a></li>
+    <li><a rel="noopener noreferrer" href="https://www.rabbitmq.com/docs" target="_blank">Documentation</a></li>
+    <li><a rel="noopener noreferrer" href="https://www.rabbitmq.com/tutorials" target="_blank">Tutorials</a></li>
+    <li><a rel="noopener noreferrer" href="https://www.rabbitmq.com/release-information" target="_blank">New releases</a></li>
     <li><a rel="noopener noreferrer" href="https://www.vmware.com/products/rabbitmq.html" target="_blank">Commercial edition</a></li>
-    <li><a rel="noopener noreferrer" href="https://www.rabbitmq.com/services.html" target="_blank">Commercial support</a></li>
+    <li><a rel="noopener noreferrer" href="https://www.rabbitmq.com/commercial-offerings" target="_blank">Commercial support</a></li>
     <li><a rel="noopener noreferrer" href="https://github.com/rabbitmq/rabbitmq-server/discussions" target="_blank">Discussions</a></li>
     <li><a rel="noopener noreferrer" href="https://rabbitmq.com/discord/" target="_blank">Discord</a></li>
-    <li><a rel="noopener noreferrer" href="https://rabbitmq.com/slack/" target="_blank">Slack</a></li>
-    <li><a rel="noopener noreferrer" href="https://www.rabbitmq.com/plugins.html" target="_blank">Plugins</a></li>
-    <li><a rel="noopener noreferrer" href="https://www.rabbitmq.com/github.html" target="_blank">GitHub</a></li>
+    <li><a rel="noopener noreferrer" href="https://www.rabbitmq.com/docs/plugins" target="_blank">Plugins</a></li>
+    <li><a rel="noopener noreferrer" href="https://www.rabbitmq.com/github" target="_blank">GitHub</a></li>
   </ul>
 </div>