[Cin] ffmpeg 7.1 is out

https://www.phoronix.com/news/FFmpeg-7.1-Released everyone parties. I ... can't figure out why we lost vf_scale in Terje's tests earlier. Hopefully just stub second parameter (?) in plugins config will restore it? Another site with more detailed changelog (and mention of second stream support for vf_scale) is currently down: https://jbkempf.com/blog/2024/ffmpeg-7.1.0/