libnotify module might be dropped

The libnotify module is provided in various versions by different runtimes.

Below you will find a list of runtimes and the provided libnotify versions.

Unless there is a very specific requirement, you may not need to compile it.

Thanks.

```
GNOME 49 : "*0.8.7"
GNOME 48 : "0.8.8"
GNOME 46-47 : "0.8.6"
GNOME 44-45 : "0.8.3"
GNOME 42-43 : "0.7.12"
GNOME 41 : "0.7.12"
```

(* reported)

https://github.com/flathub/com.github.KRTirtho.Spotube/blob/bc015e4da8219873a5325cbff1a2f06eba3e779b/com.github.KRTirtho.Spotube.yml#L33-L43