ci: Block all external network calls in tests (no-changelog) (#4930)

* setup nock to prevent tests from making any external requests

* mock all calls to posthog sdk

packages/cli/test/unit/Telemetry.test.ts

@@ -1,6 +1,8 @@
 import { Telemetry } from '@/telemetry';
 import config from '@/config';
 
+jest.mock('posthog-node');
+
 jest.spyOn(Telemetry.prototype as any, 'initRudderStack').mockImplementation(() => {
 	return {
 		flush: () => {},