Improvement of https://github.com/FreshRSS/FreshRSS/pull/4422
The main problem was due to `touch()` not automatically clearing the file status cache, and requiring a call to `clearstatcache()`. Example:
```
php > touch('/tmp/touch.txt');
php > echo date('c', filemtime('/tmp/touch.txt'));
2023-08-03T17:27:43+02:00
php > touch('/tmp/touch.txt');
php > echo date('c', filemtime('/tmp/touch.txt'));
2023-08-03T17:27:43+02:00
php > clearstatcache(true, '/tmp/touch.txt');
php > echo date('c', filemtime('/tmp/touch.txt'));
2023-08-03T17:28:21+02:00
```
4039f6c9a4