How to uninstall a PHP extension?

Let's take kjdev/lz4 as an example:

```shell
pie install kjdev/lz4

pie uninstall kjdev/lz4
# No package found: kjdev/lz4

pie uninstall lz4
# Requested package name "lz4" is invalid; it should contain a forward slash, like "vendor/package".

pie uninstall ext-lz4
# Requested package name "ext-lz4" is invalid; it should contain a forward slash, like "vendor/package".
```

Am I missing something?