Update ffmpeg and groovy-all

Hi:

It would be good to update this:

ffmpeg
groovy-all

The youtubedl plugin uses

viewtopic.php?f=20&t=18816

And so far it is the best plugin to youtube, because it is easier to use the plugin youtube

But the plugin requires updated versions of these programs.

I tested these latest versions as of today:

ffmpeg: ffmpeg version N-74179-g9dcaae7
groovy-all 2.4.4

And I have not had problems in the reproduction of videos.

Even that would be good to include the latest version of youtube-dl:

http://rg3.github.io/youtube-dl/

greetings