developer: infrastructure: remove ubuntu-runner.forgejo.org

It is no longer useful as explained at:

https://codeberg.org/forgejo-contrib/snap/pulls/10#issuecomment-2041440

docs/developer/infrastructure.md

@@ -67,6 +67,12 @@ sudo apt-get install certbot python3-certbot-nginx
 sudo certbot -n --agree-tos --email contact@forgejo.org -d example.com --nginx
 ```
 
+When removing a configuration, the certificate can also be removed with:
+
+```
+sudo certbot delete --cert-name example.com
+```
+
 ### Forgejo example
 
 ```
@@ -579,19 +585,3 @@ with `nft -f /root/code.nftables`.
 The website https://forgejo.org is hosted at
 https://uberspace.de/. The https://codeberg.org/forgejo/website/ CI
 has credentials to push HTML pages there.
-
-## ubuntu-runner.forgejo.org
-
-The ubuntu-runner.forgejo.org virtual machine is hosted in the OVH
-public cloud under the same account as the domain names. It is
-dedicated to a [Forgejo runner for the benefit of the snap package](https://codeberg.org/forgejo-contrib/snap/issues/9) of
-Forgejo.
-
-As of April 2024 it is unclear how to run snapd in an LXC nested
-container. When [this is resolved](https://code.forgejo.org/forgejo/lxc-helpers/issues/24), the machine can be destroyed and the
-runner moved to an LXC container instead.
-
-Forgejo contributors with SSH access to this machine are:
-
-- https://codeberg.org/popey
-- https://codeberg.org/earl-warren