test: replace anonymous closure functions with arrow functions

In `test/parallel/test-fs-truncate-fd.js`, callbacks use anonymous closure functions. It is safe to replace them with arrow functions since these callbacks don't alter their context (`this`). This results in shorter functions. PR-URL: #24478 Reviewed-By: Gireesh Punathil <[email protected]> Reviewed-By: James M Snell <[email protected]> Reviewed-By: Franziska Hinkelmann <[email protected]> Reviewed-By: Sakthipriyan Vairamani <[email protected]> Reviewed-By: Colin Ihrig <[email protected]>

Author: sagirk

test/parallel/test-fs-truncate-fd.js

@@ -16,12 +16,12 @@ const msg = 'Using fs.truncate with a file descriptor is deprecated.' +
 
 
 common.expectWarning('DeprecationWarning',msg,'DEP0081');
-fs.truncate(fd,5,common.mustCall(function(err){
+fs.truncate(fd,5,common.mustCall((err)=>{
 assert.ok(!err);
 assert.strictEqual(fs.readFileSync(filename,'utf8'),'hello');
 }));
 
-process.on('exit',function(){
+process.on('exit',()=>{
 fs.closeSync(fd);
 fs.unlinkSync(filename);
 console.log('ok');