test: replace fixturesDir with fixtures.path

PR-URL: https://github.com/nodejs/node/pull/15994
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

test/parallel/test-regress-GH-1899.js

@@ -1,11 +1,11 @@
 'use strict';
-const common = require('../common');
-const path = require('path');
+require('../common');
+const fixtures = require('../common/fixtures');
 const assert = require('assert');
 const spawn = require('child_process').spawn;
 
 const child = spawn(process.argv[0], [
-  path.join(common.fixturesDir, 'GH-1899-output.js')
+  fixtures.path('GH-1899-output.js')
 ]);
 let output = '';