multimedia/wl-screenrec: unbreak build with ffmpeg 8

thread 'main' panicked at cargo-crates/ffmpeg-sys-next-7.0.2/build.rs:1321:10:
Unable to generate bindings: ClangDiagnostic("fatal error: '/usr/include/libavcodec/avfft.h' file not found\n")

PR: 289032
Reported by: diizzy