avdev/jack: remove duplicated dispatch macros

The macros were moved to compat/dispatch_semaphore/semaphore.h after a libav merge, and were never removed from jack.c

libavdevice/jack.c

@@ -35,16 +35,6 @@
 #include "timefilter.h"
 #include "avdevice.h"
 
-#if HAVE_DISPATCH_DISPATCH_H
-#include <dispatch/dispatch.h>
-#define sem_t dispatch_semaphore_t
-#define sem_init(psem,x,val)  *psem = dispatch_semaphore_create(val)
-#define sem_post(psem)                dispatch_semaphore_signal(*psem)
-#define sem_wait(psem)                dispatch_semaphore_wait(*psem, DISPATCH_TIME_FOREVER)
-#define sem_timedwait(psem, val)      dispatch_semaphore_wait(*psem, dispatch_walltime(val, 0))
-#define sem_destroy(psem)             dispatch_release(*psem)
-#endif
-
 /**
  * Size of the internal FIFO buffers as a number of audio packets
  */