docs: Update archive changelog about the logilab heptapod instance

Related to T3597

docs/archive-changelog.rst

@@ -14,9 +14,13 @@ in this document for historical reasons.
 2021
 ----
 
+* **2021-09-23** Completed first archival of the `Heptapod instance
+  <https://forge.extranet.logilab.fr/>_`. Regular crawling for those repositories
+  enabled (tracking: `T3597 <https://forge.softwareheritage.org/T3597>`_)
+
 * **2021-09-23** Completed first archival of the `Heptapod instance
   <https://heptapod.host>_`. Regular crawling for those repositories enabled (tracking:
-  `T3581 <https://forge.softwareheritage.org/T3600>`_)
+  `T3600 <https://forge.softwareheritage.org/T3600>`_)
 
 * **2021-09-22** Completed first archival of the `Heptapod instance
   <https://foss.heptapod.net>_`. This is the first forge with mostly mercurial origins.