test: refactor test-crypto-pbkdf2

* re-order require() and crypto check per test writing guide
* use common.mustNotCall() to confirm callback is not invoked

PR-URL: nodejs#13975
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>

test/parallel/test-crypto-pbkdf2.js

@@ -1,11 +1,12 @@
 'use strict';
 const common = require('../common');
-const assert = require('assert');
 
 if (!common.hasCrypto) {
   common.skip('missing crypto');
   return;
 }
+
+const assert = require('assert');
 const crypto = require('crypto');
 
 //
@@ -98,7 +99,7 @@ assert.doesNotThrow(() => {
 });
 
 assert.throws(() => {
-  crypto.pbkdf2('password', 'salt', 8, 8, common.noop);
+  crypto.pbkdf2('password', 'salt', 8, 8, common.mustNotCall());
 }, /^TypeError: The "digest" argument is required and must not be undefined$/);
 
 assert.throws(() => {