test: remove common.localhostIPv6

common.localhostIPv6 is almost entirely unused and is unnecessary.
Remove it.

PR-URL: https://github.com/nodejs/node/pull/34373
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Trivikram Kamat <trivikr.dev@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/common/index.js

@@ -776,8 +776,6 @@ const common = {
     return localhostIPv4;
   },
 
-  get localhostIPv6() { return '::1'; },
-
   // opensslCli defined lazily to reduce overhead of spawnSync
   get opensslCli() {
     if (opensslCli !== null) return opensslCli;

test/sequential/test-net-connect-local-error.js

@@ -14,10 +14,10 @@ const optionsIPv4 = {
 };
 
 const optionsIPv6 = {
-  host: common.localhostIPv6,
+  host: '::1',
   port: common.PORT + 2,
   localPort: common.PORT + 3,
-  localAddress: common.localhostIPv6
+  localAddress: '::1',
 };
 
 function onError(err, options) {