test: replace fixturesDir with common.fixtures

PR-URL: #16051
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>

test/parallel/test-internal-modules.js

@@ -1,13 +1,13 @@
 'use strict';
-const common = require('../common');
-const path = require('path');
+require('../common');
+const fixtures = require('../common/fixtures');
 const assert = require('assert');
 
 assert.throws(function() {
   require('internal/freelist');
 }, /^Error: Cannot find module 'internal\/freelist'$/);
 
 assert.strictEqual(
-  require(path.join(common.fixturesDir, 'internal-modules')),
+  require(fixtures.path('internal-modules')),
   42
 );