gnu: ffmpeg: Promote version 5 to the default.

* gnu/packages/video.scm (ffmpeg): Alias to FFMPEG-5.
(mlt-6)[inpust]: Replace "ffmpeg" with FFMPEG-4.
(transcode, libquicktime, ffmpegthumbnailer, mplayer, obs,
simplescreenrecorder, handbrake, ffms2, libopenshot, wlstream)[inputs]: Change
from FFMPEG to FFMPEG-4.
* gnu/packages/arcan.scm (arcan)[inputs]: Likewise.
* gnu/packages/astronomy.scm (stackistry, libskry)[inputs]: Likewise.
* gnu/packages/audio.scm (aubio, bs1770gain)[inputs]: Likewise.
* gnu/packages/education.scm (openboard)[inputs]: Likewise.
* gnu/packages/emulators.scm (dolphin-emu, retroarch, pcsxr, ppsspp)[inputs]:
Likewise.
* gnu/packages/game-development.scm (warsow-qfusion)[inputs]: Likewise.
* gnu/packages/games.scm (oshu, hedgewars)[inputs]: Likewise.
* gnu/packages/gnunet.scm (libextractor)[inputs]: Likewise.
* gnu/packages/graphics.scm (openscenegraph)[inputs]: Likewise.
* gnu/packages/image-processing.scm (opencv, paraview-5.9)[inputs]: Likewise.
* gnu/packages/julia-jll.scm (julia-ffmpeg-jll)[inputs]: Likewise.
* gnu/packages/kde-multimedia.scm (kid3)[inputs]: Likewise.
* gnu/packages/kodi.scm (kodi)[inputs]: Likewise.
* gnu/packages/linphone.scm (mediastreamer2)[inputs]: Likewise.
* gnu/packages/linux.scm (pipewire)[inputs]: Likewise.
(pipewire-0.3)[inputs]: Replace "ffmpeg" with FFMPEG.
* gnu/packages/mp3.scm (chromaprint)[inputs]: Change from FFMPEG to FFMPEG-4.
* gnu/packages/music.scm (musikcube)[inputs]: Likewise.
* gnu/packages/rdesktop.scm (freerdp)[inputs]: Likewise.
* gnu/packages/qt.scm (qtwebengine-5)[inputs]: Likewise.

gnu/packages/kde-multimedia.scm

@@ -334,7 +334,7 @@ This package is part of the KDE multimedia module.")
     (native-inputs
      (list docbook-xsl
            extra-cmake-modules
-           ffmpeg
+           ffmpeg-4
            kdoctools
            libxslt
            python-wrapper