lavfi: remove now unused args parameter from AVFilter.init

libavfilter/af_aformat.c

libavfilter/af_amix.c

libavfilter/af_asyncts.c

libavfilter/af_channelmap.c

libavfilter/af_channelsplit.c

libavfilter/af_join.c

libavfilter/af_volume.c

libavfilter/avfilter.c

libavfilter/avfilter.h

libavfilter/buffersrc.c

libavfilter/fifo.c

libavfilter/split.c

libavfilter/vf_aspect.c

libavfilter/vf_boxblur.c

libavfilter/vf_cropdetect.c

libavfilter/vf_delogo.c

libavfilter/vf_drawbox.c

libavfilter/vf_drawtext.c

libavfilter/vf_fade.c

libavfilter/vf_format.c