test: switch to fixtures module

In test-file-read-noexist, switch from common.fixturesDir to the
fixtures module.

PR-URL: #15880
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

test/parallel/test-file-read-noexist.js

@@ -1,10 +1,10 @@
 'use strict';
 const common = require('../common');
+const fixtures = require('../common/fixtures');
 const assert = require('assert');
-const path = require('path');
 const fs = require('fs');
 
-const filename = path.join(common.fixturesDir, 'does_not_exist.txt');
+const filename = fixtures.path('does_not_exist.txt');
 fs.readFile(filename, 'latin1', common.mustCall(function(err, content) {
   assert.ok(err);
   assert.strictEqual(err.code, 'ENOENT');