test: remove unused variable

PR-URL: #17187
Reviewed-By: Anatoli Papirovski <apapirovski@mac.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Gireesh Punathil <gpunathi@in.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/sequential/test-timers-block-eventloop.js

@@ -16,7 +16,7 @@ const t3 =
   setTimeout(common.mustNotCall('eventloop blocked!'), platformTimeout(200));
 
 setTimeout(function() {
-  fs.stat('/dev/nonexistent', (err, stats) => {
+  fs.stat('/dev/nonexistent', () => {
     clearInterval(t1);
     clearInterval(t2);
     clearTimeout(t3);