changelog: fix sphinx markup error in sourceforge entry

docs/archive-changelog.rst

@@ -10,12 +10,14 @@ archival policies in the Software Heritage Archive. Each of them might have
 anomalies or other changes in archival behavior over time. They are collected
 in this document for historical reasons.
 
+
 2021
 ----
 
 * **2021-07-22** Completed first archival of SourceForge Git and Subversion
-repositories; regular crawling for those repositories enabled (tracking: `T3374
-<https://forge.softwareheritage.org/T3374>`__)
+  repositories; regular crawling for those repositories enabled (tracking:
+  `T3374 <https://forge.softwareheritage.org/T3374>`__)
+
 
 2020
 ----