avfilter: remove usage of empty header

Signed-off-by: Paul B Mahol <onemda@gmail.com>

libavfilter/f_sendcmd.c

@@ -30,7 +30,6 @@
 #include "libavutil/parseutils.h"
 #include "avfilter.h"
 #include "internal.h"
-#include "avfiltergraph.h"
 #include "audio.h"
 #include "video.h"
 

libavfilter/f_zmq.c

@@ -29,7 +29,6 @@
 #include "libavutil/opt.h"
 #include "avfilter.h"
 #include "internal.h"
-#include "avfiltergraph.h"
 #include "audio.h"
 #include "video.h"
 

libavfilter/graphdump.c

@@ -25,7 +25,6 @@
 #include "libavutil/bprint.h"
 #include "libavutil/pixdesc.h"
 #include "avfilter.h"
-#include "avfiltergraph.h"
 #include "internal.h"
 
 static int print_link_prop(AVBPrint *buf, AVFilterLink *link)

libavfilter/internal.h

@@ -26,7 +26,6 @@
 
 #include "libavutil/internal.h"
 #include "avfilter.h"
-#include "avfiltergraph.h"
 #include "formats.h"
 #include "framepool.h"
 #include "framequeue.h"