drop webhook_base_url setting from python model

It's unused

Author: Mic92

buildbot_nix/buildbot_nix/models.py

@@ -263,7 +263,6 @@ class BuildbotNixConfig(BaseModel):
     db_url: str
     build_systems: list[str]
     domain: str
-    webhook_base_url: str
     url: str
 
     use_https: bool = False

nixosModules/master.nix

@@ -768,7 +768,6 @@ in
                 eval_max_memory_size = cfg.evalMaxMemorySize;
                 eval_worker_count = cfg.evalWorkerCount;
                 domain = cfg.domain;
-                webhook_base_url = cfg.webhookBaseUrl;
                 use_https = cfg.useHTTPS;
                 outputs_path = cfg.outputsPath;
                 url = config.services.buildbot-nix.master.webhookBaseUrl;