I have a similar thing on one of my projects. Commit from 4 years ago, last updated on June 06 2023. I used the Projects API command to see the actual date/time that the last update occurred. I checked under Manage → Activity and obviously it’s completely empty. No commits, no issues, no wiki, nothing has been done on the project.
Now, since I haven’t done any changes, I then decided to check what I was doing on or around that time by checking my log files. I expected potentially that I updated my system, and Gitlab was updated and some queued processes in Gitlab were responsible for it. Perhaps migrations or whatever.
Anyway, on June 05 2023 at around 20:07 I had completed upgrade to Gitlab 16.0.2 which you can see here:
2023-06-05 20:01:51 startup archives unpack
2023-06-05 20:02:00 upgrade gitlab-ce:amd64 16.0.1-ce.0 16.0.2-ce.0
2023-06-05 20:02:00 status half-configured gitlab-ce:amd64 16.0.1-ce.0
2023-06-05 20:02:00 status unpacked gitlab-ce:amd64 16.0.1-ce.0
2023-06-05 20:02:00 status half-installed gitlab-ce:amd64 16.0.1-ce.0
2023-06-05 20:05:19 status unpacked gitlab-ce:amd64 16.0.2-ce.0
2023-06-05 20:05:44 startup packages configure
2023-06-05 20:05:44 configure gitlab-ce:amd64 16.0.2-ce.0 <none>
2023-06-05 20:05:44 status unpacked gitlab-ce:amd64 16.0.2-ce.0
2023-06-05 20:05:44 status half-configured gitlab-ce:amd64 16.0.2-ce.0
2023-06-05 20:07:35 status installed gitlab-ce:amd64 16.0.2-ce.0
therefore I expect that perhaps your Gitlab was upgraded recently prior to the last update time, and Gitlab’s scheduled tasks via cron/sidekiq were responsible for that.