composer install fails

Hi, installing via composer does fail:

```
    Install of indieweb/mention-client failed
 6/6 [============================] 100%
In Filesystem.php line 406:
  copy(/home/user/source/blog-intercon/src/vendor/composer/0da08b2d/indieweb-mention-client-php-6807f4b/phpunit): Failed to open stream: No such file or directory
```

Tried on Ubuntu 22.04 with PHP 8.1 and composer 2.8.8.