yadif: remove plugin, there's now deinterlace method=yadif

yadif: remove plugin, there's now deinterlace method=yadif

Plugin code was still the GPL version, and the
functionality has now been moved into the deinterlace
element in gst-plugins-good as method=yadif (and LGPL).

See https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/444
and https://gitlab.freedesktop.org/gstreamer/gst-plugins-good/-/merge_requests/621

Closes https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/issues/216
Fixes https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/issues/463

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/1336>