libmfx is no longer supported

https://github.com/Intel-Media-SDK/MediaSDK

DISCONTINUATION OF PROJECT.
This project will no longer be maintained by Intel.
This project has been identified as having known security escapes.
Intel has ceased development and contributions including, but not limited to,
maintenance, bug and security fixes, new releases, or updates, to this project.
Intel no longer accepts patches to this project.
If you have an ongoing need to use this project, are interested in
independently developing it, or would like to maintain patches for the open
source software community, please create your own fork of this project.
[...]

Let's get rid of it, i.e. remove the support from the following affected
packages

libavfilter7_110
libavutil56_70
libavcodec58_134
--> ffmpeg-4

vlc-noX
--> vlc

libavfilter8
libavutil57
libavcodec59
--> ffmpeg-5

gstreamer-plugins-bad
--> gstreamer-plugins-bad

Then drop libmfx package (includes libmfx-samples subpackage).