test: update V8 flag in test

--expose-debug-as is deprecated in V8, switch test-preload.js to a flag
that still exists.

PR-URL: #10917
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>

test/parallel/test-preload.js

@@ -139,10 +139,9 @@ childProcess.exec(nodeBinary + ' ' +
 
 // https://github.com/nodejs/node/issues/1691
 process.chdir(common.fixturesDir);
-childProcess.exec(nodeBinary + ' ' +
-  '--expose_debug_as=v8debug ' +
-  '--require ' + fixture('cluster-preload.js') + ' ' +
-  'cluster-preload-test.js',
+childProcess.exec(
+  nodeBinary + ' ' + '--expose_natives_as=v8natives ' + '--require ' +
+    fixture('cluster-preload.js') + ' ' + 'cluster-preload-test.js',
   function(err, stdout, stderr) {
     if (err) throw err;
     assert.ok(/worker terminated with code 43/.test(stdout));