test: replace fixturesDir with common.fixtures

PR-URL: https://github.com/nodejs/node/pull/15973
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>

test/parallel/test-http2-respond-file-fd.js

@@ -1,11 +1,11 @@
 'use strict';
 
 const common = require('../common');
+const fixtures = require('../common/fixtures');
 if (!common.hasCrypto)
   common.skip('missing crypto');
 const http2 = require('http2');
 const assert = require('assert');
-const path = require('path');
 const fs = require('fs');
 
 const {
@@ -13,7 +13,7 @@ const {
   HTTP2_HEADER_CONTENT_LENGTH
 } = http2.constants;
 
-const fname = path.resolve(common.fixturesDir, 'elipses.txt');
+const fname = fixtures.path('elipses.txt');
 const data = fs.readFileSync(fname);
 const stat = fs.statSync(fname);
 const fd = fs.openSync(fname, 'r');