test: replace equal with strictEqual in test-freelist.js

Improving asserts in test-freelist.js

PR-URL: https://github.com/nodejs/node/pull/9910
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-freelist.js

@@ -6,8 +6,8 @@ require('../common');
 const assert = require('assert');
 const freelist = require('internal/freelist');
 
-assert.equal(typeof freelist, 'object');
-assert.equal(typeof freelist.FreeList, 'function');
+assert.strictEqual(typeof freelist, 'object');
+assert.strictEqual(typeof freelist.FreeList, 'function');
 
 const flist1 = new freelist.FreeList('flist1', 3, String);