Fix link to pgarchives project

This also makes a small modification to the language describing
how to get involved in the project.

Co-authored-by: Tobias Bussmann <[email protected]>

Author: jkatz

templates/pages/developer/related-projects.html

@@ -83,10 +83,11 @@ <h3>pgarchives</h3>
       the PostgreSQL project.
     </p>
     <ul>
-      <li><a href="https://git.postgresql.org/gitweb/?p=pgweb.git;a=summary">Dynamic content repository</a></li>
+      <li><a href="https://git.postgresql.org/gitweb/?p=pgarchives.git;a=summary">pgarchives main repository</a></li>
+      <li><a href="https://www.postgresql.org/list/">Mailing list archives</a></li>
     </ul>
     <p>
-      You can get involved in this project by communicating on
+      You can get involved with these projects by communicating on
       the <a href="mailto:[email protected]">pgsql-www</a> mailing
       list.
     </p>