Fix no_proxy test (#28131)

Co-authored-by: Jerry Lin <jerrysf@google.com>

Author: jerrylin3321

packages/core/src/utils/fetch.test.ts

@@ -261,6 +261,7 @@ describe('fetch utils', () => {
     it('should fall back to no_proxy if NO_PROXY is not set', () => {
       const proxyUrl = 'http://proxy.example.com';
       const noProxyValue = 'localhost,127.0.0.1';
+      vi.stubEnv('NO_PROXY', undefined);
       vi.stubEnv('no_proxy', noProxyValue);
 
       setGlobalProxy(proxyUrl);