rtpdec: Don't explicitly include unistd.h any longer

unistd.h used to be required for gethostname. On windows, gethostname
is provided by winsock2.h. Now network.h includes both unistd.h and
winsock2.h if they exist.
Signed-off-by: Martin Storsjö <martin@martin.st>

libavformat/rtpdec.c

@@ -26,7 +26,6 @@
 #include "mpegts.h"
 #include "url.h"
 
-#include <unistd.h>
 #include "network.h"
 
 #include "rtpdec.h"