test: fix typo in test-tls-cnnic-whitelist

PR-URL: #19662
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

test/parallel/test-tls-cnnic-whitelist.js

@@ -14,7 +14,7 @@ function loadPEM(n) {
 }
 
 const testCases = [
-  { // Test 0: for the check of a cert not existed in the whitelist.
+  { // Test 0: for the check of a cert not in the whitelist.
     // agent7-cert.pem is issued by the fake CNNIC root CA so that its
     // hash is not listed in the whitelist.
     // fake-cnnic-root-cert has the same subject name as the original