test: refactor test-fs-watch-non-recursive

The test was duplicating some functionality in the `tmpdir` module.

PR-URL: nodejs#25386
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/pummel/test-fs-watch-non-recursive.js

@@ -25,19 +25,13 @@ const path = require('path');
 const fs = require('fs');
 
 const tmpdir = require('../common/tmpdir');
+tmpdir.refresh();
 
 const testDir = tmpdir.path;
 const testsubdir = path.join(testDir, 'testsubdir');
 const filepath = path.join(testsubdir, 'watch.txt');
 
-function cleanup() {
-  try { fs.unlinkSync(filepath); } catch { }
-  try { fs.rmdirSync(testsubdir); } catch { }
-}
-process.on('exit', cleanup);
-cleanup();
-
-try { fs.mkdirSync(testsubdir, 0o700); } catch {}
+fs.mkdirSync(testsubdir, 0o700);
 
 // Need a grace period, else the mkdirSync() above fires off an event.
 setTimeout(function() {