test: remove experimental-wasm-threads flag

It is already true by default in V8.

Refs: v8/v8@be9ff65
PR-URL: #45074
Reviewed-By: Richard Lau <[email protected]>
Reviewed-By: Antoine du Hamel <[email protected]>
Reviewed-By: Colin Ihrig <[email protected]>
Reviewed-By: James M Snell <[email protected]>
Reviewed-By: Tobias Nießen <[email protected]>

Author: targos

test/parallel/test-worker-message-port-wasm-threads.js

@@ -1,4 +1,3 @@
-// Flags: --experimental-wasm-threads
 'use strict';
 const common = require('../common');
 const assert = require('assert');