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