fix: avoid instanceof MockNotMatchedError (#4474)

Author: Uzlopak

lib/mock/mock-utils.js

@@ -367,7 +367,7 @@ function buildMockDispatch () {
       try {
         mockDispatch.call(this, opts, handler)
       } catch (error) {
-        if (error instanceof MockNotMatchedError) {
+        if (error.code === 'UND_MOCK_ERR_MOCK_NOT_MATCHED') {
           const netConnect = agent[kGetNetConnect]()
           if (netConnect === false) {
             throw new MockNotMatchedError(`${error.message}: subsequent request to origin ${origin} was not allowed (net.connect disabled)`)