fix: use temporal's assertNever instead of a custom one

connectors/src/connectors/zendesk/temporal/workflows.ts

@@ -1,4 +1,5 @@
 import type { ModelId } from "@dust-tt/types";
+import { assertNever } from "@temporalio/common/lib/type-helpers";
 import {
   executeChild,
   proxyActivities,
@@ -29,14 +30,6 @@ const {
   startToCloseTimeout: "1 minute",
 });
 
-function assertNever(x: never): never {
-  throw new Error(
-    `${
-      typeof x === "object" ? JSON.stringify(x) : x
-    } is not of type never. This should never happen.`
-  );
-}
-
 /**
  * Sync Workflow for Zendesk.
  * This workflow is responsible for syncing all the help centers and tickets for a given connector.
@@ -85,7 +78,7 @@ export async function zendeskSyncWorkflow({
           break;
         }
         default:
-          assertNever(signal.type);
+          assertNever("Unknown signal type.", signal.type);
       }
     });
   });