Explicitly suppress filesystem error on `forget()`

When forgetting a cache key that doesn't exist in the filesystem an error will be thrown if error suppression fails.

As per `Illuminate\Filesystem\Filesystem` (:128)

```php
foreach ($paths as $path) { if ( ! @unlink($path)) $success = false; }
```

Where `@unlink` error suppression fails, resulting exception:
```
dev.ERROR: exception 'ErrorException' with message 'unlink(/app/storage/cache/e1/76/e1768c1bb7ebb703a94dc92669bcdacf): No such file or directory' in /vendor/laravel/framework/src/Illuminate/Filesystem/Filesystem.php:128
```

This PR will update the driver to check the file existence first because there is no instance (afaik) where the user would want to see this error message.