Updated debian changelog for version 1.9.0

debian/changelog

+swh-vault (1.9.0-1~swh1) unstable-swh; urgency=medium
+
+  * New upstream release 1.9.0     - (tagged by Valentin Lorentz
+    <vlorentz@softwareheritage.org> on 2023-09-18 10:28:20 +0200)
+  * Upstream changes:     - v1.9.0     - * to_disk: Represent revisions
+    as empty directories instead of symlinks     - * interface: Add
+    download_url method and implement it in backend
+
+ -- Software Heritage autobuilder (on jenkins-debian1) <jenkins@jenkins-debian1.internal.softwareheritage.org>  Mon, 18 Sep 2023 08:32:54 +0000
+
 swh-vault (1.8.2-1~swh1) unstable-swh; urgency=medium
 
   * New upstream release 1.8.2     - (tagged by Antoine Lambert