fix(ops/gerrit-webhook-to-irccat): fix json parsing

patchset and change numbers are numbers in the JSON, trying to deserialize them into a string fails:

Jul 28 20:34:03 gerrit01 gerrit-webhook-to-irccat[2430441]: time=2025-07-28T20:34:03.675Z level=WARN msg="failed to parse body" error="json: cannot unmarshal number into Go struct field PatchSet.patchSet.number of type string"

Update our library dependency to a version containing the fixed types.

Also add tests for the three messages we care about.

Change-Id: Iac44e6ad01a8590b4cafa4d301c9f45000f335d0
Reviewed-on: https://cl.snix.dev/c/snix/+/30624
Tested-by: besadii
Reviewed-by: Ryan Lahfa <ryan@lahfa.xyz>
Reviewed-by: Jade Lovelace <jade@lix.systems>
Autosubmit: Florian Klink <flokli@flokli.de>
Reviewed-by: Florian Klink <flokli@flokli.de>

ops/gerrit-webhook-to-irccat/default.nix

@@ -10,5 +10,5 @@ pkgs.buildGoModule {
       ./go.sum
     ];
   };
-  vendorHash = "sha256-Xq0p6EEPFS23H+RMkzQw6767d8WujAz7doR6E/YKrgY=";
+  vendorHash = "sha256-i7EpH9/2FGZwhn4VHP32aL13M07fd+cbUhzddYi5XfE=";
 }