test: add missing tmpdir.refresh() in recently-added test

Without `tmpdir.refresh()`, the test fails in some situations. This was
missed because using `test.py` will almost always result in a leftover
tmpdir lying around that makes the `refresh()` not needed.

Refs: #24913 (comment)

PR-URL: #25098
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Daijiro Wachi <daijiro.wachi@gmail.com>
Reviewed-By: Anto Aravinth <anto.aravinth.cse@gmail.com>

Author: Trott

test/parallel/test-child-process-spawn-args.js

@@ -12,6 +12,8 @@ const { spawn } = require('child_process');
 const common = require('../common');
 const tmpdir = require('../common/tmpdir');
 
+tmpdir.refresh();
+
 const command = common.isWindows ? 'cd' : 'pwd';
 const options = { cwd: tmpdir.path };