avenc_mpeg2video:Apply the patch for breaking some encoders

avenc_mpeg2video:Apply the patch for breaking some encoders

- https://github.com/GStreamer/gstreamer/commit/5372b77987cbdf16f681526152325bee8388ab62
Revert "avvidenc: Set timebase in the ffmpeg context to nanoseconds a…
…nd set framerate"

This reverts commit 50db594.

This broke the MPEG-1 video encoder as it requires the framerate to be
used for the timebase.

Fixes https://gitlab.freedesktop.org/gstreamer/gstreamer/-/issues/1734
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/3780>

Change-Id: I40383d874e929d1eade6f586e5a977631d4d556e