test: add callback to fs.close() in test-fs-chmod

To avoid '[DEP0013] DeprecationWarning:
Calling an asynchronous function without callback is deprecated.'

PR-URL: #12795
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-fs-chmod.js

@@ -114,7 +114,7 @@ fs.open(file2, 'a', common.mustCall((err, fd) => {
       assert.strictEqual(mode_sync, fs.fstatSync(fd).mode & 0o777);
     }
 
-    fs.close(fd);
+    fs.close(fd, assert.ifError);
   }));
 }));