change citation to the new citation page

Author: hossam26644

python/tskit/util.py

@@ -663,7 +663,7 @@ def tree_sequence_html(ts):
                 </div>
             </div>
             <div style="margin-top: 1em; font-size: 0.8em; text-align: center;">
-                To cite this software, please consult the citation manual: <a href="https://tskit.dev/tskit/docs/stable/citation.html" target="_blank">tskit.dev/tskit/docs/stable/citation.html</a>
+                To cite this software, please consult the citation manual: <a href="https://tskit.dev/citation/" target="_blank">https://tskit.dev/citation/</a>
             </div>
         </div>
     """  # noqa: B950