grub: mention that team#40185 is considered fixed

howto/upgrades.md

@@ -170,6 +170,10 @@ it is blocked. to upgrade, make sure the install device is defined, by
 running `dpkg-reconfigure grub-pc`. this issue might actually have
 been fixed in the package, see [issue 40185](https://gitlab.torproject.org/tpo/tpa/team/-/issues/40185).
 
+Update: this issue has been resolved and grub upgrades are now
+automated. This section is kept for historical reference, or in case
+the upgrade path is broken again.
+
 ## user@ services
 
 Services setup with the new systemd-based startup system documented in