fate: change the scenecut fate threshold

why change .4 to .25, it's for:
one scenecut(pkt_pts=20040) isn't detected by 0.4 threshold

why not change to 0.3 instead of 0.25:
it will miss the scenecut(pkt_pts=20040) after applying the next
patch which enables yuvj420

for fate testing, it's better to catch all scenecut scenes.
Reviewed-by: Marton Balint <cus@passwd.hu>
Signed-off-by: Limin Wang <lance.lmwang@gmail.com>

tests/fate/filter-video.mak

@@ -734,7 +734,7 @@ SCENEDETECT_DEPS = FFPROBE LAVFI_INDEV MOVIE_FILTER SELECT_FILTER SCALE_FILTER \
                    AVCODEC AVDEVICE MOV_DEMUXER SVQ3_DECODER ZLIB
 FATE_METADATA_FILTER-$(call ALLYES, $(SCENEDETECT_DEPS)) += fate-filter-metadata-scenedetect
 fate-filter-metadata-scenedetect: SRC = $(TARGET_SAMPLES)/svq3/Vertical400kbit.sorenson3.mov
-fate-filter-metadata-scenedetect: CMD = run $(FILTER_METADATA_COMMAND) "sws_flags=+accurate_rnd+bitexact;movie='$(SRC)',select=gt(scene\,.4)"
+fate-filter-metadata-scenedetect: CMD = run $(FILTER_METADATA_COMMAND) "sws_flags=+accurate_rnd+bitexact;movie='$(SRC)',select=gt(scene\,.25)"
 
 CROPDETECT_DEPS = FFPROBE LAVFI_INDEV MOVIE_FILTER CROPDETECT_FILTER SCALE_FILTER \
                   AVCODEC AVDEVICE MOV_DEMUXER H264_DECODER

tests/ref/fate/filter-metadata-scenedetect

@@ -7,4 +7,5 @@ pkt_pts=9760|tag:lavfi.scene_score=1.000000
 pkt_pts=14080|tag:lavfi.scene_score=0.838916
 pkt_pts=15700|tag:lavfi.scene_score=1.000000
 pkt_pts=18500|tag:lavfi.scene_score=0.474948
+pkt_pts=20040|tag:lavfi.scene_score=0.379700
 pkt_pts=21760|tag:lavfi.scene_score=1.000000