test: skip --title check on IBM i

Similar to SmartOS IBM i does not return the process.title

PR-URL: #53952
Fixes: #53852
Reviewed-By: Richard Lau <rlau@redhat.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/fixtures/spawn-worker-with-copied-env.js

@@ -2,7 +2,7 @@
 
 // This test is meant to be spawned with NODE_OPTIONS=--title=foo
 const assert = require('assert');
-if (process.platform !== 'sunos') {  // --title is unsupported on SmartOS.
+if (process.platform !== 'sunos' && process.platform !== 'os400') {  // --title is unsupported on SmartOS and IBM i.
   assert.strictEqual(process.title, 'foo');
 }