ffmpeg: add missing includes to pipewiregrab patch

The formats.h and video.h header files are needed by the patch but were
not explicitly included. They are implicitly included via internal.h
in FFmpeg 6.0.1 (the version we currently use in the daemon), but not in
later versions (6.1+). (Thanks to Maxim Cournoyer for bringing this
problem to my attention.)

Change-Id: I99f35fa351f6aeca2091a6ee7c267acec0cb08bb

contrib/src/ffmpeg/pipewiregrab-source-filter.patch

@@ -72,10 +72,10 @@ index d7db46c2af..87204fec71 100644
  extern const AVFilter ff_vsrc_smptebars;
 diff --git a/libavfilter/vsrc_pipewiregrab.c b/libavfilter/vsrc_pipewiregrab.c
 new file mode 100644
-index 0000000000..ff9c3468ab
+index 0000000000..3ffe38b52f
 --- /dev/null
 +++ b/libavfilter/vsrc_pipewiregrab.c
-@@ -0,0 +1,1373 @@
+@@ -0,0 +1,1375 @@
 +/*
 + * PipeWire input grabber (ScreenCast)
 + * Copyright (C) 2024 Savoir-faire Linux, Inc.
@@ -127,7 +127,9 @@ index 0000000000..ff9c3468ab
 +#include "libavformat/internal.h"
 +#include "libavutil/avassert.h"
 +#include "avfilter.h"
++#include "formats.h"
 +#include "internal.h"
++#include "video.h"
 +
 +#include <pipewire/pipewire.h>
 +#include <pipewire/thread-loop.h>