rspamd not configured correctly in current "ubuntu-22" branch (and possibly master)

Steps to reproduce

• Setup an Ubuntu 22.04 minimal VM image and ssh into it
• cd /tmp
• git clone https://git.ispconfig.org/ispconfig/ispconfig-autoinstaller.git
• cd ispconfig-autoinstaller
• git checkout ubuntu-22
• ./ispc3-ai.sh --channel=dev --use-ftp-ports=40110-40210 --unattended-upgrades=autoclean,reboot
• reboot the VM

Correct behaviour

https://$MYHOSTNAME:8081/rspamd/ should show the rspamd login page.

What happens instead

Error 500.

==> /var/log/apache2/error.log <== [Fri Nov 04 14:35:37.762675 2022] [proxy:warn] [pid 13376:tid 139972304660032] [client 79.196.157.23:38548] AH01144: No protocol handler was valid for the URL /rspamd/ (scheme 'http'). If you are using a DSO version of mod_proxy, make sure the proxy submodules are included in the configuration using LoadModule.

==> /var/log/apache2/other_vhosts_access.log <== static.66.234.12.49.clients.your-server.de:8081 79.196.157.23 - - [04/Nov/2022:14:35:37 +0100] "GET /rspamd/ HTTP/2.0" 500 650 "-" "Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/107.0.0.0 Safari/537.36"

Environment

See reproduction steps above.

Proposed fix

a2enmod proxy_http somewhere in ISPconfig's install procedure fixes this. Previously (stable ISPconfig releases) this was the case.