update status of gitlab labels after cleanup (e.g. gitlab#3)

howto/gitlab.md

@@ -597,8 +597,13 @@ loading the label list can take a second or more on slower links, and
 it's really hard to find the label you're looking for, which affects
 usability -- and especially discoverability -- quite a bit.
 
-There is work underway in the [label cleanup](https://gitlab.torproject.org/ahf/label-cleanup/-/tree/main/) repository to
-rewrite and delete labels in one batch for all the projects.
+ahf performed a major label cleanup operation on 2020-06-27, following
+the specification in the [label cleanup](https://gitlab.torproject.org/ahf/label-cleanup/-/tree/main/) repository. It rewrote and
+deleted labels in one batch in all projects. When the job was done,
+[empty labels](https://gitlab.torproject.org/ahf/label-cleanup/-/blob/main/tpo/core/tor-delete.txt) were removed as well.
+
+A [dump of the previous state](https://gitlab.torproject.org/ahf/label-cleanup/-/raw/main/tpo/core/tor-history.yaml) is available for historical
+purposes.
 
 ### Project organisation