[bug#61117] Update svtplay-dl to 4.18

[Leo Famulari <leo@famulari.name>]

Thanks again for working on this package!

On Sat, Jan 28, 2023 at 01:33:44PM +0100, Tobias Geerinckx-Rice via Guix-patches via wrote:
> > I've also moved ffmpeg form inputs to propagated-inputs
> 
> Please avoid propagation whenever possible; it breaks all kinds of nice
> things.

I'm here to express my weak preference for dynamically binding FFmpeg in
use cases like this one.

That means, I prefer if packages like svtplay-dl do not depend on FFmpeg
at all, but rather expect the user to install FFmpeg alongside them.

I prefer this because I use a custom FFmpeg professionally as a video
engineer, and it's easier to use it with Guix packages if the dependency
is resolved at run-time rather than at build-time.

I'd expect that many people like me also use a variety of custom FFmpeg
builds for different use cases.

Like I said, it's a weak preference. And I probably wouldn't use
svtplay-dl at work in the US, although I do use youtube-dl / yt-dlp. Let
me know what you think.