warning fix: remove duplicate typedef for 'instance_t'

I chose to remove it from common/utils/itti/itti_types.h,
maybe it's not the correct solution.

common/utils/itti/itti_types.h

@@ -71,7 +71,5 @@ typedef struct {
 #define INSTANCE_DEFAULT    (UINT16_MAX - 1)
 #define INSTANCE_ALL        (UINT16_MAX)
 
-typedef uint16_t instance_t;
-
 #endif