fate: fix ffmpeg-attached_pics test dependencies

Signed-off-by: Marton Balint <cus@passwd.hu>

tests/fate/ffmpeg.mak

@@ -31,7 +31,7 @@ FATE_FFMPEG-$(call ALLYES, AEVALSRC_FILTER ASETNSAMPLES_FILTER AC3_FIXED_ENCODER
 fate-ffmpeg-filter_complex_audio: CMD = framecrc -filter_complex "aevalsrc=0:d=0.1,asetnsamples=1537" -c ac3_fixed
 
 # Ticket 6375
-FATE_SAMPLES_FFMPEG-$(call ALLYES, MOV_DEMUXER ALAC_DECODER ALAC_ENCODER) += fate-ffmpeg-attached_pics
+FATE_SAMPLES_FFMPEG-$(call ALLYES, MOV_DEMUXER PNG_DECODER ALAC_DECODER ALAC_ENCODER) += fate-ffmpeg-attached_pics
 fate-ffmpeg-attached_pics: CMD = threads=2 framecrc -i $(TARGET_SAMPLES)/lossless-audio/inside.m4a -acodec alac -max_muxing_queue_size 16
 
 FATE_SAMPLES_FFMPEG-$(CONFIG_COLORKEY_FILTER) += fate-ffmpeg-filter_colorkey