nixos/tests/matrix-appservice-irc: disable registration verification

The test would previously error out like this:

> synapse_homeserver[1155]: synapse.config._base.ConfigError: You have
> enabled open registration without any verification. This is a known
> vector for spam and abuse. If you would like to allow public
> registration, please consider adding email, captcha, or token-based
> verification. Otherwise this check can be removed by setting the
> `enable_registration_without_verification` config option to `true`.

(cherry picked from commit 1d2a0b8)

nixos/tests/matrix-appservice-irc.nix

@@ -19,6 +19,11 @@ import ./make-test-python.nix ({ pkgs, ... }:
 
             enable_registration = true;
 
+            extraConfig = ''
+              # don't use this in production, always use some form of verification
+              enable_registration_without_verification: true
+            '';
+
             listeners = [
               # The default but tls=false
               {