test: move require http2 to after crypto check

Currently test-http2-client-write-empty-string.js will throw "Error
[ERR_NO_CRYPTO]: Node.js is not compiled with OpenSSL crypto support"
when configured --without-ssl.

This commit moves the require of http2 to after the crypto check to
avoid this error.

PR-URL: nodejs#19111
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Jon Moss <me@jonathanmoss.me>

test/parallel/test-http2-client-write-empty-string.js

@@ -1,12 +1,13 @@
 'use strict';
 
 const assert = require('assert');
-const http2 = require('http2');
 
 const common = require('../common');
 if (!common.hasCrypto)
   common.skip('missing crypto');
 
+const http2 = require('http2');
+
 for (const chunkSequence of [
   [ '' ],
   [ '', '' ]