[Gitea] update the update script

[EV21]

config

• hide version number, so this info is only visable at /admin or via CLI

update script changes

• I refactored a few things,
• removed some checks (they were actually added for debug reasons) as the issues should be fixed by the fix_stop_signal function,
• fixed a bug in the version comparator so it is not a tautology
• ignore versions with pre-release code words, this is maybe important for Forgejo, but it looks like they now publish their pre-releases in another repository, so maybe a slightly changed version of this script (API requests) can be used for Forgejo,
• handle expired PGP keys

deploy preview 👀

[noave]

thanks, the update script is quite complex and it would be nicer to have it in a separate repository (maybe with a responsible maintainer). But for now we don't have a process for that and this way it keeps in sync with the guide itself.