test: 修正 mock 的滥用情况

src/services/mcp/__tests__/channelPermissions.test.ts

@@ -1,8 +1,5 @@
 import { mock, describe, expect, test } from "bun:test";
 
-mock.module("src/utils/slowOperations.js", () => ({
-  jsonStringify: (v: unknown) => JSON.stringify(v),
-}));
 mock.module("src/services/analytics/growthbook.js", () => ({
   getFeatureValue_CACHED_MAY_BE_STALE: () => false,
 }));